* config/alpha/alpha.c (struct machine_function): New flag for VMS,
	uses_condition_handler.
	(alpha_expand_builtin_establish_vms_condition_handler): New expander.
	(alpha_expand_builtin_revert_vms_condition_handler): New expander.
	(enum alpha_builtin): New ALPHA_BUILTIN_REVERT_VMS_CONDITION_HANDLER
	and ALPHA_BUILTIN_ESTABLISH_VMS_CONDITION_HANDLER values.
	(code_for_builtin): New insn codes for the new alpha_builtins.
	(alpha_init_builtins): Register the new functions as BUILT_IN_MD.
	(alpha_sa_size): Account for uses_condition_handler.
	(alpha_expand_prologue): Likewise.
	(alpha_start_function): Likewise.
	(alpha_expand_epilogue): Likewise.
	* config/alpha/alpha-protos.h: Prototype the new alpha.c builtin
	establish/revert expanders.
	* config/alpha/alpha.h (DWARF_FRAME_REGNUM): Define.
	* config/alpha/alpha.md	(builtin_establish_vms_condition_handler):
	New expander, resorting to the alpha.c associated function.
	(builtin_revert_vms_condition_handler): Likewise.
	* config/alpha/vms-gcc_shell_handler.c: New file. Implements
	__gcc_shell_handler, the static VMS condition handler used as
	an indirection wrapper to the current dynamically established
	handler.
	* config/alpha/vms-unwind.h: Complete rewrite.
	* config/alpha/t-vms (LIB2FUNCS_EXTRA): Add vms-gcc_shell_handler.c
	* config/alpha/vms.h (MD_UNWIND_SUPPORT):
	

Co-Authored-By: Douglas B Rupp <rupp@gnat.com>

From-SVN: r150612