kvx: Improve lexing & parsing

Up until now, we used ENV.PROMOTE_IMMEDIATE to get the next candidates,
however this candidate can be directly extracted from the array (in
kvx-parse.h) registering all the immediates.

During lexing, we ignored trailing characters after a number, this is
not good enough since now number can be followed by a modifier.  The
function READ_TOKEN and GET_TOKEN_CLASS have been update to take this
into account.

gas/ChangeLog:

	* config/kvx-parse.c (promote_token): Do not rely on
	  env.promote_immediate anymore.
	(get_token_class): Do not ignore trailing characters after a
	number.
	(read_token): Likewise.
	(print_token_list): THIS SHOULD NOT BE HERE.