Make liborcus -fvisibility setting consistent with LO one

Esp. since LO links against a liborcus.a, this would otherwise cause linker
warnings like

  ld: warning: direct access in orcus::orcus_xml::read_file(char const*) to
  global weak symbol boost::unordered_detail::prime_list_template<unsigned
  long>::value means the weak symbol cannot be overridden at runtime. This was
  likely caused by different translation units being compiled with different
  visibility settings.

on Mac OS X (where HAVE_GCC_VISIBILITY_FEATURE is unset).

Change-Id: I6f09b61aa77b6d5c3f8b53407d8faff4fb3bb8a1

liborcus/UnpackedTarball_liborcus.mk

@@ -26,6 +26,10 @@ ifeq ($(OS),MACOSX)
 liborcus_patches += liborcus_0.1.0-tac.patch
 endif
 
+ifneq ($(HAVE_GCC_VISIBILITY_FEATURE),TRUE)
+liborcus_patches += visibility.patch
+endif
+
 # <https://gitorious.org/orcus/orcus/merge_requests/2#
 # f60d6eecee72349993a392a9a63ddf3383d3b8c8-
 # f60d6eecee72349993a392a9a63ddf3383d3b8c8@2>:

liborcus/visibility.patch

+--- configure
++++ configure
+@@ -3211,7 +3211,7 @@
+ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+ 
+-CXXFLAGS="$CXXFLAGS -O2 -fvisibility=hidden -Wall"
++CXXFLAGS="$CXXFLAGS -O2 -Wall"
+ 
+ # ===========================
+ # Find required base packages