Implement .func/.endfunc pseudo-ops.

	Implement .func/.endfunc pseudo-ops.
	* read.h (stabs_generate_asm_func,stabs_generate_asm_endfunc): Declare.
	(s_func): Declare.
	* read.c (potable): Add .func,.endfunc.
	(s_func): New function.
	* stabs.c (stabs_generate_asm_func,stabs_generate_asm_endfunc): New
	functions.
	(in_doc_func_p,current_function_label): New static globals.
	(stabs_generate_asm_lineno): Emit function relative stabs if in .func.