terminal-left: terminal window's left position
terminal-top: terminal window's top position
terminal-width: terminal window's width
terminal-height: terminal window's height
* grub-core/gfxmenu/theme-loader.c: Likewise.
* include/grub/gfxmenu_view.h: Likewise.
* po/exlude.pot: Likewise.
* grub-core/gfxmenu/view.c: Likewise.
Also updated minimal window size.
Also terminal_sanity_check function has been introduced.