Corrected big mistake with default weapon dmgs

The arrays which held the default weapon damage information were
misordered, and were lacking data for a large number of weapons.
Removed some unnecessary files.
Restored and moved null/win_main.cpp for MP.

Restored the null/win_main.cpp file for MP and moved it into the win32/ folder.
Fixed the COM_Begin/EndParsingSession functions.

So the COM_EndParsingSession function is quite useful after all. It is
indeed needed as there are some places in the code where parsing sessions need to nest
(one example is in the UI_LoadMenus function, which eventually calls
UI_ParseMenu. Both of these functions require their own parsing session).
I've added some extra debug-only code in COM_BeginParseSession which will
throw a fatal error if there are too many nested parsing sessions
(currently hardcoded to 2).
Moved default renderer name into a #define.
Ported some filesystem changes from MP to SP.

Mainly the code to do with fs_homepath, so save files are now saved in the
user's home directory. I think this means SP config files are also saved
in the home directory as well.
Windows now uses Sys_LoadDll to load renderer.

Also copied across the fix from MP to unload the renderer library when it
gets shutdown.
Unregister window class when shutting down GLimp.

This is a fix ported over from MP again.
Fixed problem with g_wv not existing?!
Corrected ordering of characters in INT_ID macro.

Sorry, this will break save games again. In short, a multi character
constant 'ABCD' should have 'A' as the highest bits, and 'D' as the lowest
bits. Before it was the other way around.
Added _PORTABLE_VERSION to SP code.

This allows portable versions of the SP code to be built (portable as in,
the home/user directory is not used for reading/writing files as in the
new system). I've also added a CMake switch to allow this to be toggled
(BuildPortableVersion).
Corrected some more uses of COM_EndParseSession.

Also increased the maximum nested parsing sessions as this is needed at
the mission selection screen.
Removed error when failing to load EFX in SP.
Fix #275 - removed unused files.

These are the last few files to remove from the code which are not used. If they need to be recovered, then you can run the following:

git checkout $(git rev-list -n 1 HEAD -- "<filename here>")^ -- "<filename here>"

Command taken from http://stackoverflow.com/questions/953481/restore-a-deleted-file-in-a-git-repo
Fix SP hud loading fallback so that it doesn't error before trying to load fallback.
Fixed SP hud loading not freeing file handle early enough if file was too big.
Fixed incorrect memset sizeof usage in SP.
sizeof( &itemInfo ) should have been sizeof( *itemInfo )
Don't assign menu pointer to item parent in Item_Paint unless item is not null first.
Sort cvars in config files alphabetically
Disable Cvar_Set2 developer printf in SP.
Port r_mapOverBrightBits over to SP.