Remove response files in msvc.compile.c++ action.

Relax check for msvc 6.0, so that simple "6" is matched.

Patches from Olaf Janssen.


[SVN r29477]

tools/build

@@ -1 +1 @@
-Subproject commit 838dcd5222218197cb71a2220d2702727274864d
+Subproject commit f007a99d937377f20d7df6d725837341771fc886