Remove old lint code

Remove old lint code

This removes dead code that, according to the comments, existed to
placate lint.  I don't think this has been relevant in a long time,
and certainly not since gdb switched to C++.

Tested by rebuilding.

ChangeLog
2018-07-30  Tom Tromey  <tom@tromey.com>

	* cli/cli-decode.c (lookup_cmd): Remove lint code.
	* value.c (unpack_long): Remove lint code.
	* valops.c (value_ind): Remove lint code.
	* valarith.c (value_x_binop, value_x_unop, value_equal)
	(value_pos): Remove lint code.