Remove initialize_utils

Remove initialize_utils

initialize_utils only registers some commands, so it isn't necessary
to run it at any particular time during startup.  This patch removes
it and merges its contents into _initialize_utils.

Tested by the buildbot.

gdb/ChangeLog
2019-09-26  Tom Tromey  <tom@tromey.com>

	* utils.h (initialize_utils): Don't declare.
	* top.c (gdb_init): Don't call initialize_utils.
	* utils.c (initialize_utils): Remove.  Move contents...
	(_initialize_utils): ... here.