Update fltk to 1.4.0rc3

INSTALL.md

@@ -12,7 +12,7 @@ You will need [Microsoft Visual Studio](https://visualstudio.microsoft.com/vs/);
 
 #### Setting up FLTK
 
-1. Clone [fltk release-1.4.0rc2](https://github.com/fltk/fltk/tree/release-1.4.0rc2) into lib\\**fltk**. (ie, `git clone -b release-1.4.0rc2 https://github.com/fltk/fltk.git lib/fltk`)
+1. Clone [fltk release-1.4.0rc3](https://github.com/fltk/fltk/tree/release-1.4.0rc3) into lib\\**fltk**. (ie, `git clone -b release-1.4.0rc3 https://github.com/fltk/fltk.git lib/fltk`)
 2. Open Visual Studio, select **Open a local folder**, and open the lib\fltk folder. This will automatically generate the CMake project with a configuration named **x64-Debug**.
 3. Create the following additional configurations with the appropriate **Configuration Type** of either Debug or Release: x64-Release, x86-Debug, and x86-Release. For x64 configurations, make sure the **Toolset** is set to **msvc_x64_x64**. For x86 configurations, make sure the Toolset is set to **msvc_x86_x64**. For all 4 configurations, uncheck the **FLTK_GRAPHICS_GDIPLUS** option.
 4. Set the configuration to **x86-Release**.
@@ -89,7 +89,7 @@ git clone https://github.com/dannye/crystal-tracker.git
 cd crystal-tracker
 
 # Build FLTK 1.4.0
-git clone -b release-1.4.0rc2 https://github.com/fltk/fltk.git lib/fltk
+git clone -b release-1.4.0rc3 https://github.com/fltk/fltk.git lib/fltk
 pushd lib/fltk
 cmake -D CMAKE_INSTALL_PREFIX="$(realpath "$PWD/../..")" -D CMAKE_BUILD_TYPE=Release -D FLTK_GRAPHICS_CAIRO=1 -D FLTK_BACKEND_WAYLAND=0
 make