genemit: Split insn-emit.cc into several partitions.

genemit: Split insn-emit.cc into several partitions.

On riscv insn-emit.cc has grown to over 1.2 mio lines of code and
compiling it takes considerable time.
Therefore, this patch adjust genemit to create several partitions
(insn-emit-1.cc to insn-emit-n.cc).  The available patterns are
written to the given files in a sequential fashion.

Similar to match.pd a configure option --with-emitinsn-partitions=num
is introduced that makes the number of partition configurable.

gcc/ChangeLog:

	PR bootstrap/84402
	PR target/111600

	* Makefile.in: Handle split insn-emit.cc.
	* configure: Regenerate.
	* configure.ac: Add --with-insnemit-partitions.
	* genemit.cc (output_peephole2_scratches): Print to file instead
	of stdout.
	(print_code): Ditto.
	(gen_rtx_scratch): Ditto.
	(gen_exp): Ditto.
	(gen_emit_seq): Ditto.
	(emit_c_code): Ditto.
	(gen_insn): Ditto.
	(gen_expand): Ditto.
	(gen_split): Ditto.
	(output_add_clobbers): Ditto.
	(output_added_clobbers_hard_reg_p): Ditto.
	(print_overload_arguments): Ditto.
	(print_overload_test): Ditto.
	(handle_overloaded_code_for): Ditto.
	(handle_overloaded_gen): Ditto.
	(print_header): New function.
	(handle_arg): New function.
	(main): Split output into 10 files.
	* gensupport.cc (count_patterns): New function.
	* gensupport.h (count_patterns): Define.
	* read-md.cc (md_reader::print_md_ptr_loc): Add file argument.
	* read-md.h (class md_reader): Change definition.