test that sized deallocation really works before enabling it

Weirdly, some OSX compiler does allow -fsized-deallocation, yet barks
on any attempt to actually use it at compile time (!). So lets detect
this as well in configure and opt out as necessary.

Should fix issue gperftools#870.

configure.ac

@@ -358,9 +358,11 @@ AC_CACHE_CHECK([if C++ compiler supports -fsized-deallocation],
                [AC_LANG_PUSH(C++)
                 OLD_CXXFLAGS="$CXXFLAGS"
                 CXXFLAGS="$CXXFLAGS -fsized-deallocation"
-                AC_COMPILE_IFELSE([AC_LANG_PROGRAM(,)],
-                                  perftools_cv_sized_deallocation_result=yes,
-                                  perftools_cv_sized_deallocation_result=no)
+                AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+                    [[#include <new>]],
+                    [[(::operator delete)(0, 256)]])],
+                 perftools_cv_sized_deallocation_result=yes,
+                 perftools_cv_sized_deallocation_result=no)
                 CXXFLAGS="$OLD_CXXFLAGS"
                 AC_LANG_POP(C++)])