gdb: remove language.h include from frame.h

gdb: remove language.h include from frame.h

This helps resolve some cyclic include problem later in the series.
The only language-related thing frame.h needs is enum language, and that
is in defs.h.

Doing so reveals that a bunch of files were relying on frame.h to
include language.h, so fix the fallouts here and there.

Change-Id: I178a7efec1953c2d088adb58483bade1f349b705
Reviewed-By: Bruno Larsen <blarsen@redhat.com>