Also make build_complex_cproj available globally and use
it for the existing match.pd rules.

Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.

gcc/
	* builtins.c (fold_builtin_cproj): Delete.
	(fold_builtin_1): Handle constant arguments here.
	(build_complex_cproj): Move and rename to...
	* tree.c: (build_complex_inf): ...this.
	* tree.h (build_complex_inf): Declare.
	* match.pd: Fold cproj(x)->x if x has no infinity.
	Use build_complex_inf for existing cproj rules.

From-SVN: r229164