Use Win32 instead of Windows in Doxygen headings

This was especially bad in the window guide, where the TOC ended up
having "Window related hints" and "Windows specific window hints" close
to one another.

This commit only fixes headings.  There are likely issues in the actual
text as well.

docs/compile.dox

@@ -278,7 +278,7 @@ __GLFW_VULKAN_STATIC__ determines whether to use the Vulkan loader linked
 directly with the application.  This is disabled by default.
 
 
-@subsection compile_options_win32 Windows specific CMake options
+@subsection compile_options_win32 Win32 specific CMake options
 
 @anchor GLFW_BUILD_WIN32
 __GLFW_BUILD_WIN32__ determines whether to include support for Win32 when compiling the

docs/window.dox

@@ -447,7 +447,7 @@ The no error mode for OpenGL and OpenGL ES is described in detail by the
 extension.
 
 
-@subsubsection window_hints_win32 Windows specific window hints
+@subsubsection window_hints_win32 Win32 specific hints
 
 @anchor GLFW_WIN32_KEYBOARD_MENU_hint
 __GLFW_WIN32_KEYBOARD_MENU__ specifies whether to allow access to the window
@@ -455,7 +455,7 @@ menu via the Alt+Space and Alt-and-then-Space keyboard shortcuts.  This is
 ignored on other platforms.
 
 
-@subsubsection window_hints_osx macOS specific window hints
+@subsubsection window_hints_osx macOS specific hints
 
 @anchor GLFW_COCOA_RETINA_FRAMEBUFFER_hint
 __GLFW_COCOA_RETINA_FRAMEBUFFER__ specifies whether to use full resolution