Test for PCH

	* BoostBuild.py (Tester.copy_preserving_timestap): New.
	* pch.py: New.
	* test_all.py: Register pch.py on gcc.


[SVN r35512]

tools/build

@@ -1 +1 @@
-Subproject commit c9f08718a94a0304888bad7994d63f9eb37cb337
+Subproject commit 1d1ab035c1ba31ab17b35677aaaef69068357528