Use yy-remap.h in cp-name-parser.y

This changes cp-name-parser.y to use yy-remap.h, rather than its old
manual approach.

This required declaring parser_fprintf in cp-name-parser.y.
parser-defs.h can't be included here because parser-defs.h declares a
global "lexptr", which conflicts with the local one in
cp-name-parser.y.  This is only temporary, and will be cleaned up
later in the series.

gdb/ChangeLog
2018-06-01  Tom Tromey  <tom@tromey.com>

	* cp-name-parser.y (parser_fprintf): Declare.
	(GDB_YY_REMAP_PREFIX): Define.
	Include yy-remap.h.  Don't redefine yy* identifiers.