Use the CF-CFString.h, F-NS*.h proxy headers where needed in the objective-c
testsuite.  Make minor adjustments to tests as required, providing that those
do not alter the test intent.

2019-06-15  Iain Sandoe  <iain@sandoe.co.uk>

	PR objc/90709
	* objc.dg/encode-7-next-64bit.m: Use proxy headers.
	* objc.dg/image-info.m: Likewise.
	* objc.dg/method-6.m: Likewise.
	* objc.dg/no-extra-load.m: Likewise.
	* objc.dg/objc-foreach-4.m: Likewise.
	* objc.dg/objc-foreach-5.m: Likewise.
	* objc.dg/proto-lossage-7.m: Likewise.
	* objc.dg/strings/const-cfstring-2.m: Likewise.
	* objc.dg/strings/const-cfstring-5.m: Likewise.
	* objc.dg/strings/const-str-12b.m: Likewise.
	* objc.dg/symtab-1.m: Likewise.
	* objc.dg/torture/strings/const-cfstring-1.m: Likewise.
	* objc.dg/torture/strings/const-str-10.m: Likewise.
	* objc.dg/torture/strings/const-str-11.m: Likewise.
	* objc.dg/torture/strings/const-str-9.m: Likewise.
	* objc.dg/zero-link-1.m: Likewise.
	* objc.dg/zero-link-2.m: Likewise.
	* objc.dg/zero-link-3.m: Likewise.
	* objc.dg/isa-field-1.m: Suppress unwanted warning, add comment why.
	* objc.dg/headers.m: XFAIL for Darwin14-19.
	* objc.dg/objc-gc-4.m: Skip for Darwin > 16, the API use is an error
	there.

From-SVN: r272326