Replace match.pd DEFINE_MATH_FNs with auto-generated lists

Replace match.pd DEFINE_MATH_FNs with auto-generated lists

This patch autogenerates the operator lists for maths functions
like SQRT, adding an additional entry for internal functions.
E.g.:

        (define_operator_list SQRT
            BUILT_IN_SQRTF
            BUILT_IN_SQRT
            BUILT_IN_SQRTL
            IFN_SQRT)

and:

        (define_operator_list CABS
            BUILT_IN_CABSF
            BUILT_IN_CABS
            BUILT_IN_CABSL
            null)

(since there's no internal function for CABS).

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

gcc/
	* Makefile.in (MOSTLYCLEANFILES): Add cfn-operators.pd.
	(generated_files): Likewise.
	(s-cfn-operators, cfn-operators.pd): New rules.
	(s-match): Depend on cfn-operators.pd.
	* gencfn-macros.c: Expand comment to describe -o behavior.
	(print_define_operator_list): New function.
	(main): Accept -o.  Call print_define_operator_list.
	* genmatch.c (main): Add the current directory to the include path.
	* match.pd (DEFINE_MATH_FN): Delete.  Include cfn-operators.pd
	instead.

From-SVN: r230486