r_fillWindowAlphaChan is a hack to work around an older issue with
Wayland/Mesa, which has been fixed in Mesa 24.1 (and also seems to work
with current NVIDIA drivers). Additionally, in SDL3 the EGL-specific
(and thus mostly only affecting Wayland)
SDL_HINT_VIDEO_EGL_ALLOW_TRANSPARENCY has been replaced with the generic
SDL_PROP_WINDOW_CREATE_TRANSPARENT_BOOLEAN (that could also affect
other platforms), so it's harder to enable this only for Wayland.
I think most people using SDL3 will use a recent Mesa/driver versions,
so I don't enable it by default for SDL3 (SDL2 behaves like before).
However, with `r_fillWindowAlphaChan 1` the hack can be enabled anyway
(r_fillWindowAlphaChan defaults to "-1" which means "let dhewm3 decide
whether to enable this")
The defines in idlib/Str.h won't be set to redirect the low
level c string functions to idStr when IDSTR_NO_REDIRECT is
set.
Fixes compilation for MSVC:
error C2761: 'Cmp' : member function redeclaration not allowed
Reported by spiral.
Get rid of the 2 CPUID flags and combine them with SSE in one
implementation.
SSE flags can now be set on all x86 and x86_64 platforms -
independent of -ffast-math.
Helper defines borrowed from STREFLOP.
