Introduce gimple_eh_dispatch

Introduce gimple_eh_dispatch

This corresponds to:
  [PATCH 30/89] Introduce gimple_eh_dispatch
  https://gcc.gnu.org/ml/gcc-patches/2014-04/msg01236.html
from the original 89-patch kit

That earlier patch was approved by Jeff:
> OK after fixing up the naming/const stuff as discussed for prior
> patches.
> That applies to 22-30. Make sure to take care of
> the pretty printers per Trevor's comments as well. He indicated those
> were missing in a couple of those patches.
in https://gcc.gnu.org/ml/gcc-patches/2014-05/msg00628.html

gcc/
	* coretypes.h (gimple_eh_dispatch): New typedef.
	(const_gimple_eh_dispatch): New typedef.

	* gimple-pretty-print.c (dump_gimple_eh_dispatch): Require a
	gimple_eh_dispatch rather than a plain gimple.
	(pp_gimple_stmt_1): Add a checked cast to gimple_eh_dispatch
	within GIMPLE_EH_DISPATCH case of switch statement.

	* gimple-streamer-in.c (input_gimple_stmt): Likewise.

	* gimple-streamer-out.c (output_gimple_stmt): Likewise.

	* gimple.c (gimple_build_eh_dispatch): Return a gimple_eh_dispatch
	rather than a plain gimple.

	* gimple.h (gimple_build_eh_dispatch): Return a gimple_eh_dispatch
	rather than a plain gimple.
	(gimple_eh_dispatch_region): Require a const_gimple_eh_dispatch
	rather than a plain const_gimple.
	(gimple_eh_dispatch_set_region): Require a gimple_eh_dispatch
	rather than a plain gimple.

	* tree-cfg.c (make_edges): Add a checked cast to gimple_eh_dispatch
	within GIMPLE_EH_DISPATCH case of switch statement.
	(gimple_verify_flow_info): Likewise.
	(gimple_redirect_edge_and_branch): Likewise.
	(move_stmt_r): Likewise, adding a local.

	* tree-eh.c (emit_eh_dispatch): Convert local from gimple to
	gimple_eh_dispatch.
	(make_eh_dispatch_edges): Require a gimple_eh_dispatch rather than
	a plain gimple.
	(redirect_eh_dispatch_edge): Likewise.
	(lower_eh_dispatch): Likewise.
	(execute_lower_eh_dispatch): Add a checked cast to
	gimple_eh_dispatch.
	(mark_reachable_handlers): Likewise.
	(verify_eh_dispatch_edge): Require a gimple_eh_dispatch rather
	than a plain gimple.

	* tree-eh.h (make_eh_dispatch_edges): Likewise.
	(redirect_eh_dispatch_edge): Likewise.
	(verify_eh_dispatch_edge): Likewise.

	* tree-inline.c (remap_gimple_stmt): Add a checked cast to
	gimple_eh_dispatch within GIMPLE_EH_DISPATCH case of switch
	statement, adding a local.
	(copy_edges_for_bb): Add a checked cast to gimple_eh_dispatch.