Uncomment conflict fields from pkg-config files.

The referenced bug was fixed in 2007 and has been released in pkg-config-0.23
(16.Jan.2008). The fixed version is widely available.
diff --git a/protobuf.pc.in b/protobuf.pc.in
index 29f2487..4901490 100644
--- a/protobuf.pc.in
+++ b/protobuf.pc.in
@@ -9,6 +9,4 @@
 Libs: -L${libdir} -lprotobuf @PTHREAD_CFLAGS@ @PTHREAD_LIBS@
 Libs.private: @LIBS@
 Cflags: -I${includedir} @PTHREAD_CFLAGS@
-# Commented out because it crashes pkg-config *sigh*:
-#   http://bugs.freedesktop.org/show_bug.cgi?id=13265
-# Conflicts: protobuf-lite
+Conflicts: protobuf-lite