The assembler incorrectly recognised "c" as a register name, and
refused to allow it where it expected a symbol/label.

gas/
	* config/tc-s12z.c (lex_reg_name): Compare the length of the strings
	before the contents.
	* testsuite/gas/s12z/labels.d: New file.
	* testsuite/gas/s12z/labels.s: New file.
	* testsuite/gas/s12z/s12z.exp: Add them.