Remove init_cli_cmds

Remove init_cli_cmds

I noticed that init_cli_cmds only installs a command, and so doesn't
need to be handled specially.  This patch merges it into
_initialize_cli_cmds.

The help text is constructed dynamically, which is sometimes an
indication that special treatment is needed; but in this case it is
just to insert the value of "gdbinit", which is created at
compile-time and not modified; so this doesn't affect the result.

This version also removes the "gdbinit" global.  There's no need for
it, as GDBINIT can be used instead.  Note, though, that the help text
in question must still be dynamically constructed, in order to be
i18n-friendly.

gdb/ChangeLog
2019-07-11  Tom Tromey  <tromey@adacore.com>

	* main.c (get_init_files): Use GDBINIT, not gdbinit.
	* auto-load.c (file_is_auto_load_safe): Use GDBINIT, not gdbinit.
	* top.h (gdbinit): Don't declare.
	* cli/cli-cmds.c (init_cli_cmds): Remove, merging contents
	into...
	(_initialize_cli_cmds): ...here.  Use GDBINIT, not gdbinit.
	* top.c (gdb_init): Don't call init_cli_cmds.
	(gdbinit): Remove.
	* cli/cli-cmds.h (init_cli_cmds): Don't declare.