Exclude .svn (and other "dot" directories) when installing headers.

My fix for PR15820 in r180132 inadvertently removed the exclusion for ".*".
This puts it back again. Thanks for Nico Weber for pointing this out!

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@203807 91177308-0d34-0410-b5e6-96231b3b80d8

Makefile

@@ -34,7 +34,8 @@ clean::
 installheaders::
 	mkdir -p $(HEADER_DIR)/c++/v1/ext
 	(cd $(SRCDIRS)/include && \
-	  tar cf - --exclude=support --exclude=CMakeLists.txt .) | \
+	  tar cf - --exclude=".*" --exclude=support \
+	           --exclude=CMakeLists.txt *) | \
 	  (cd $(HEADER_DIR)/c++/v1 && tar xf -)
 	chmod 755 $(HEADER_DIR)/c++/v1
 	chmod 644 $(HEADER_DIR)/c++/v1/*