gas: tc-tic54x.c hash tables

Cleaning up the subsym_hash memory is a real pain.  Keys and values
entered into the table are quite diverse.  In some cases the key is
allocated and thus needs to be freed, in others the key is a const
string.  Values are similar, and in some cases not even a string.
Tidy this by inserting a new subsym_ent_t that describes key/value
type.  This meant the math_hash table was no longer needed.  The patch
also tidies how math functions are called, those that are supposed to
return int now no longer return their value in a float.

	* config/tc-tic54x.c (math_hash): Delete.
	(subsym_proc_entry): Move earlier, make proc a union, merge with..
	(math_proc_entry): ..this.  Delete type.
	(math_procs): Merge into subsym_procs.
	(subsym_ent_t): New.  Use this type in subsym_hash..
	(stag_add_field_symbols, tic54x_var, tic54x_macro_info): ..here..
	(md_begin, subsym_create_or_replace, subsym_lookup): ..and here..
	(subsym_substitute): ..and here.  Adjust subsym_proc_entry
	function calls.  Free replacement when not returned.
	(subsym_get_arg): Adjust subsym_lookup.
	(free_subsym_ent, subsym_htab_create ): New functions, use when
	creating subsym_hash.
	(free_local_label_ent, local_label_htab_create): Similarly.
	(tic54x_remove_local_label): Delete.
	(tic54x_clear_local_labels): Simplify.
	(tic54x_asg): Use notes obstack to dup strings.
	(tic54x_eval): Likewise.
	(subsym_ismember): Likewise.
	(math_cvi, math_int, math_sgn): Return int.
	(tic54x_macro_start): Decrement macro_level before calling as_fatal.
	(tic54x_md_end): New function.
	* config/tc-tic54h.c (tic54x_md_end): Declare.
	(md_end): Define.