This reduces size of the next patch.

ddraw/d3d8/d3d9 only support a limited number of formats, but those already
limit the supported formats themselves.

This should be done by the context management these days.

Some of these formats can't even be translated by ddraw.

dbghelp: For mingw32 (stabs debug info), parse the FileHeader's symbol table to offset properly the global variables.

Found by Valgrind.