Add the new RGB boolean capability to terminfo to indicate we support truecolor

See https://gist.github.com/XVilka/8346728#detection

kitty/terminfo.py

@@ -31,6 +31,8 @@ bool_capabilities = {
     'xenl',
     # has extra status line (window title)
     'hs',
+    # Detect truecolor support
+    'RGB',
     # Terminfo extension used by tmux to detect true color support (non-standard)
     'Tc',
     # Indicates support for styled and colored underlines (non-standard) as
@@ -436,7 +438,7 @@ termcap_aliases.update({
 queryable_capabilities = numeric_capabilities.copy()
 queryable_capabilities.update(string_capabilities)
 extra = (bool_capabilities | numeric_capabilities.keys() | string_capabilities.keys()) - set(termcap_aliases.values())
-no_termcap_for = frozenset('Su Tc setrgbf setrgbb fullkbd'.split())
+no_termcap_for = frozenset('Su Tc setrgbf setrgbb fullkbd RGB'.split())
 if extra - no_termcap_for:
     raise Exception('Termcap aliases not complete, missing: {}'.format(extra - no_termcap_for))
 del extra

terminfo/kitty.terminfo

@@ -1,4 +1,5 @@
 xterm-kitty|KovIdTTY,
+	RGB,
 	Su,
 	Tc,
 	am,