Introduce CP_OPERATOR_STR/CP_OPERATOR_LEN and use throughout

Move LENGTH_OF_OPERATOR from cp-support.c to cp-support.h so we can
use it elsewhere.  Since there's already
CP_ANONYMOUS_NAMESPACE_STR/CP_ANONYMOUS_NAMESPACE_LEN there, follow
the same naming pattern for the new symbols.

gdb/ChangeLog:
2017-07-17  Pedro Alves  <palves@redhat.com>

	* c-exp.y (operator_stoken): Use CP_OPERATOR_LEN and
	CP_OPERATOR_STR.
	* c-typeprint.c (is_type_conversion_operator): Use
	CP_OPERATOR_STR.
	* cp-support.c (LENGTH_OF_OPERATOR): Delete.
	(cp_find_first_component_aux): Use CP_OPERATOR_STR and
	CP_OPERATOR_LEN.
	* cp-support.h (CP_OPERATOR_STR, CP_OPERATOR_LEN): New.
	* gnu-v2-abi.c (gnuv2_is_operator_name): Use CP_OPERATOR_STR.
	* gnu-v3-abi.c (gnuv3_is_operator_name): Use CP_OPERATOR_STR.
	* linespec.c (linespec_lexer_lex_string): Use CP_OPERATOR_LEN and
	CP_OPERATOR_STR.
	* location.c: Include "cp-support.h".
	(explicit_location_lex_one): Use CP_OPERATOR_LEN and
	CP_OPERATOR_STR.
	* symtab.c (operator_chars): Use CP_OPERATOR_STR and
	CP_OPERATOR_LEN.

gdb/gnu-v2-abi.c

@@ -68,7 +68,7 @@ gnuv2_is_vtable_name (const char *name)
 static int
 gnuv2_is_operator_name (const char *name)
 {
-  return startswith (name, "operator");
+  return startswith (name, CP_OPERATOR_STR);
 }