egl: SDL_EGL_LoadLibaryOnly() shouldn't set _this->gl_config.driver_loaded = 1

This is handled in in the higher-level SDL_GL_LoadLibrary().

All uses of SDL_EGL_LoadLibrary (which calls the Only version) are just
target-specific wrappers for their own GL_LoadLibrary hook, with two
exceptions which now handle driver_loaded correctly (although it's
questionable if these init-if-no-one-did-it-correctly-already code blocks
should exist at all, fwiw).

Fixes Bugzilla #5190.

extra : rebase_source : 634a9bc144b6b87c1ffade24525e269a43834db8
3 files changed