Update cogl.symbols and cogl-path.symbols

In Lionel's work for supporting introspection better for Cogl, a number of
public symbols were added for Cogl and Cogl-Path, so add these symbols to
cogl.symbols and cogl-path.symbols so that they can be exported, which will
fix the build of the Cogl conformance test and the introspection files
for the Windows-based builds.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
MSVC Builds: Don't Link to SDL Automatically

Remove #pragma directives that causes any applications that use Cogl to
link to the SDL libraries when Cogl was built with the SDL winsys.  This is
mainly due to the availability of both SDL-1.x and SDL-2.x support in the
SDL winsys, where different libraries are linked for SDL-1.x and SDL-2.x.

To avoid having to link to the SDL/SDL2 libraries when the application code
is not directly using SDL/SDL2, define SDL_MAIN_HANDLED in the CFLAGS so
that SDL's wrapper main() implementation will not be used when the
application is being built.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit c3035912833eabe1f6dadbea23c78e595aac79dc)
Visual Studio Builds: Avoid Implicit Link to SDL

Cogl, when built with the SDL winsys, includes the SDL headers in its
headers, which causes main() to be defined to SDL's main() wrapper on
Windows, which means that SDL2.lib and SDL2main.lib need to be linked to
every single program that links to Cogl with the SDL winsys.

Avoid this behavior by defining SDL_MAIN_HANDLED in the CFLAGS of the
sample and test programs, and let people know that this is the case.