tr_init: allow software rendering

This makes the game runs on virtualized macOS out of the box.

Mesa systems like Linux or FreeBSD just fallbacks on software rendering
without requiring any enablement.

We better want to get the game running at all cost than just
aborting, the user can then tweak the presets to get more
performance if that's really needed.

Author: illwieckz

src/engine/renderer/tr_init.cpp

@@ -1118,7 +1118,7 @@ ScreenshotCmd screenshotPNGRegistration("screenshotPNG", ssFormat_t::SSF_PNG, "p
 		r_glMinorVersion = Cvar_Get( "r_glMinorVersion", "", CVAR_LATCH );
 		r_glProfile = Cvar_Get( "r_glProfile", "", CVAR_LATCH );
 		Cvar::Latch( r_glDebugProfile );
-		r_glAllowSoftware = Cvar_Get( "r_glAllowSoftware", "0", CVAR_LATCH );
+		r_glAllowSoftware = Cvar_Get( "r_glAllowSoftware", "1", CVAR_LATCH );
 		r_glExtendedValidation = Cvar_Get( "r_glExtendedValidation", "0", CVAR_LATCH );
 
 		// latched and archived variables