Fix Gnome Terminal version detection
Fix Gnome Terminal version detection

(Discovered on OpenBSD.)

POSIX says that "Regular expression syntax shall be that defined in
XBD Basic Regular Expressions, [...]."

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/expr.html

lvfeng1130/gnome-terminal-colors-solarized,dlnguyen/solarized,webdev1001/gnome-terminal-colors-monokai,erikbrinkman/gnome-terminal-colors-solarized,esindril/gnome-terminal-colors-solarized,JianyuWang/gnome-terminal-colors-solarized,jaehyuk/gnome-terminal-colors,pricco/gnome-terminal-colors-monokai,ifels/gnome-terminal-colors-solarized,yitang/gnome-terminal-colors-solarized,lukepfister/gnome-terminal-colors-monokai,GregoryShen/gnome-terminal-colors-solarized,mkanai/gnome-terminal-colors-monokai