* tc-arm.c (all error messages): Normalize capitalization of messages.

* tc-arm.c (all error messages): Normalize capitalization of messages.

* tc-arm.h (md_operand): Delete define.
* tc-arm.c (in_my_get_expression): New static variable.
(my_get_expression): Set and clear it.
(md_operand): New function.  If called from my_get_expression
put the error in inst.error.
(output_inst): Now takes argument of instruction being assembled.
Print it out with any error message.
(do_ldst, do_ldstv4, thumb_load_store): Fault attempt to use a store
with '=' syntax.
(end_of_line): Don't update inst.error if it is already set.