Most files including gdbcmd.h currently rely on it to access things
actually declared in cli/cli-cmds.h (setlist, showlist, etc).  To make
things easy, replace all includes of gdbcmd.h with includes of
cli/cli-cmds.h.  This might lead to some unused includes of
cli/cli-cmds.h, but it's harmless, and much faster than going through
the 170 or so files by hand.

Change-Id: I11f884d4d616c12c05f395c98bbc2892950fb00f
Approved-By: Tom Tromey <tom@tromey.com>