t6k11: use the gint array for variant detection
r61524: use true triple buffering by default
display: define DWIDTH and DHEIGHT
display: add C_RGB(r,g,b) (0 ≤ r,g,b ≤ 31) [fxcg50]
This macro used to protect the declaration of the [vram] variable of
gint. This variable was short to keep drawing functions short but could
clutter the namespace.
That being said, it's even better to just [#define vram gint_vram] if
you need. This change renames the variable to [gint_vram], exposes it
whenever <gint/display.h> is included, and removes the GINT_NEED_VRAM
macro altogether.