Enable lexical binding in all .el files

Upstream Emacs has made lack of the directive a warning. So enable it
explicitly everywhere. It provides various benefits such as better
introspection by the compiler into the code and optimizations.

Fixes a bunch of warnings:

      Error: file has no ‘lexical-binding’ directive on its first line

purescript-align-imports.el

@@ -1,4 +1,4 @@
-;;; purescript-align-imports.el --- Align the import lines in a PureScript file
+;;; purescript-align-imports.el --- Align the import lines in a PureScript file -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2010  Chris Done
 

purescript-collapse.el

@@ -1,4 +1,4 @@
-;;; purescript-collapse.el --- Collapse expressions
+;;; purescript-collapse.el --- Collapse expressions -*- lexical-binding: t -*-
 
 ;; Copyright (c) 2014 Chris Done. All rights reserved.
 

purescript-decl-scan.el

@@ -1,4 +1,4 @@
-;;; purescript-decl-scan.el --- Declaration scanning module for PureScript Mode
+;;; purescript-decl-scan.el --- Declaration scanning module for PureScript Mode -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2004, 2005, 2007, 2009  Free Software Foundation, Inc.
 ;; Copyright (C) 1997-1998  Graeme E Moss

purescript-font-lock.el

@@ -1,4 +1,4 @@
-;;; purescript-font-lock.el --- Font locking module for PureScript Mode
+;;; purescript-font-lock.el --- Font locking module for PureScript Mode -*- lexical-binding: t -*-
 
 ;; Copyright 2003, 2004, 2005, 2006, 2007, 2008  Free Software Foundation, Inc.
 ;; Copyright 1997-1998  Graeme E Moss, and Tommy Thorn

purescript-indent.el

@@ -1,4 +1,4 @@
-;;; purescript-indent.el --- "semi-intelligent" indentation module for PureScript Mode
+;;; purescript-indent.el --- "semi-intelligent" indentation module for PureScript Mode -*- lexical-binding: t -*-
 
 ;; Copyright 2004, 2005, 2007, 2008, 2009  Free Software Foundation, Inc.
 ;; Copyright 1997-1998  Guy Lapalme

purescript-indentation.el

@@ -1,4 +1,4 @@
-;;; purescript-indentation.el -- indentation module for PureScript Mode -*- lexical-binding: t -*-
+;;; purescript-indentation.el -- indentation module for PureScript Mode -*- lexical-binding: t -*- -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2009  Kristof Bastiaensen
 

purescript-mode.el

@@ -1,4 +1,4 @@
-;;; purescript-mode.el --- A PureScript editing mode    -*- coding: utf-8 -*-
+;;; purescript-mode.el --- A PureScript editing mode    -*- coding: utf-8 lexical-binding: t -*-
 
 ;; Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008  Free Software Foundation, Inc
 ;; Copyright (C) 1992, 1997-1998  Simon Marlow, Graeme E Moss, and Tommy Thorn

purescript-move-nested.el

@@ -1,4 +1,4 @@
-;;; purescript-move-nested.el --- Change the column of text nested below a line
+;;; purescript-move-nested.el --- Change the column of text nested below a line -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2010  Chris Done
 

purescript-navigate-imports.el

@@ -1,4 +1,4 @@
-;;; purescript-navigate-imports.el --- A function for cycling through PureScript import lists
+;;; purescript-navigate-imports.el --- A function for cycling through PureScript import lists -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2010  Chris Done
 

purescript-presentation-mode.el

@@ -1,4 +1,4 @@
-;;; purescript-presentation-mode.el --- Presenting PureScript things
+;;; purescript-presentation-mode.el --- Presenting PureScript things -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013  Chris Done
 

purescript-show.el

@@ -1,4 +1,4 @@
-;;; purescript-show.el --- A pretty printer for PureScript Show values
+;;; purescript-show.el --- A pretty printer for PureScript Show values -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2011  Chris Done
 

purescript-simple-indent.el

@@ -1,4 +1,4 @@
-;;; purescript-simple-indent.el --- Simple indentation module for PureScript Mode
+;;; purescript-simple-indent.el --- Simple indentation module for PureScript Mode -*- lexical-binding: t -*-
 
 ;; Copyright (C) 1998  Heribert Schuetz, Graeme E Moss
 

purescript-sort-imports.el

@@ -1,4 +1,4 @@
-;;; purescript-sort-imports.el --- Sort the list of PureScript imports at the point alphabetically
+;;; purescript-sort-imports.el --- Sort the list of PureScript imports at the point alphabetically -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2010  Chris Done
 

purescript-str.el

@@ -1,4 +1,4 @@
-;;; purescript-str.el --- PureScript related string utilities
+;;; purescript-str.el --- PureScript related string utilities -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013  Herbert Valerio Riedel
 

purescript-string.el

@@ -1,3 +1,4 @@
+;;; purescript-string.el --- string manipulation utilties -*- lexical-binding: t -*-
 ;;;###autoload
 (defun purescript-trim (string)
   (replace-regexp-in-string

purescript-unicode-input-method.el

@@ -1,4 +1,4 @@
-;;; purescript-unicode-input-method.el --- PureScript Unicode helper functions  -*- coding: utf-8 -*-
+;;; purescript-unicode-input-method.el --- PureScript Unicode helper functions  -*- coding: utf-8 lexical-binding: t -*-
 
 ;; Copyright (C) 2010-2011  Roel van Dijk
 

purescript-utils.el

@@ -1,4 +1,4 @@
-;;; purescript-utils.el --- General utility functions used by purescript-mode modules
+;;; purescript-utils.el --- General utility functions used by purescript-mode modules -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013  Herbert Valerio Riedel
 

purescript-yas.el

@@ -1,4 +1,4 @@
-;;; purescript-yas.el --- Customization support for Luke Hoersten's yasnippets
+;;; purescript-yas.el --- Customization support for Luke Hoersten's yasnippets -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013  John Wiegley, Luke Hoersten
 

tests/haskell-sort-imports-tests.el

@@ -1,4 +1,4 @@
-;;; purescript-sort-imports-tests.el --- Unit tests for purescript-sort-imports
+;;; purescript-sort-imports-tests.el --- Unit tests for purescript-sort-imports -*- lexical-binding: t -*-
 
 ;; Copyright (c) 2014 Chris Done. All rights reserved.