rs6000, update Darwin call handling to latest scheme.

rs6000, update Darwin call handling to latest scheme.

This patch mormalises Darwin's call handling to match the scheme
recently introduced and gives it target-specific call expanders.

2018-12-12  Iain Sandoe  <iain@sandoe.co.uk>

	* config/rs6000/rs6000-protos.h (rs6000_call_darwin): New.
	(rs6000_sibcall_darwin): New. (macho_call_template): Remove.
	* config/rs6000/rs6000.c (get_prev_label): Forward declaration.
	(rs6000_call_template_1): Handle Darwin.
	(macho_call_template): Remove.
	(rs6000_call_sysv): Remove handling for Darwin.
	(rs6000_call_darwin_1, rs6000_call_darwin): New
	(rs6000_sibcall_darwin): New.
	* config/rs6000/rs6000.md (define_expand “call”): Handle Darwin
	with its own expander. (define_expand “call_value”): Likewise.
	(define_expand “sibcall”): Likewise.
	(define_expand “sibcall_value”): Likewise.
	(call_nonlocal_sysv): Remove Darwin special-casing.
	(call_value_nonlocal_sysv): Likewise.

From-SVN: r267048