[CN] Allow member_shift<ctype> as a syntax

[dc-mak]

Current one is confusing. Stop-gap for #349 . Should be a very small change to the parser, making it more similar to array_shift

cerberus/parsers/c/c_parser.mly

Lines 1860 to 1871 in ede24dc

	| CN_ARRAY_SHIFT LT ty=ctype GT LPAREN base=expr COMMA index=expr RPAREN
	{ Cerb_frontend.Cn.(CNExpr ( Cerb_location.(region ($startpos, $endpos) (PointCursor $startpos($1)))
	, CNExpr_array_shift (base, Some ty, index))) }
	| CN_ARRAY_SHIFT LPAREN base=expr COMMA index=expr RPAREN
	{ Cerb_frontend.Cn.(CNExpr ( Cerb_location.(region ($startpos, $endpos) (PointCursor $startpos($1)))
	, CNExpr_array_shift (base, None, index))) }
	| CN_MEMBER_SHIFT LPAREN base=expr COMMA member=cn_variable RPAREN
	{ Cerb_frontend.Cn.(CNExpr ( Cerb_location.(region ($startpos, $endpos) (PointCursor $startpos($1)))
	, CNExpr_membershift (base, None, member))) }
	| CN_MEMBER_SHIFT LT tag=cn_variable GT LPAREN base=expr COMMA member=cn_variable RPAREN
	{ Cerb_frontend.Cn.(CNExpr ( Cerb_location.(region ($startpos, $endpos) (PointCursor $startpos($1)))
	, CNExpr_membershift (base, Some tag, member))) }