There are two issues with the Darwin14 (SDK) headers in which unguarded
advanced syntax elements causes any code including these headers to fail.

2019-06-21  Iain Sandoe  <iain@sandoe.co.uk>

	* inclhack.def: Guard __has_attribute and __has_extension in
	os/base.h.
	Guard Apple blocks syntax in dispatch/object.h.
	* fixincl.x: Regenerate.
	* tests/base/dispatch/object.h: New file.
	* tests/base/os/base.h: New file.

From-SVN: r272561