compilerplugins: strip out -m32/-m64 from CXX

These are not part of LO and need to be built with native bitness
of the compiler.

Change-Id: I41fdec130a63e0c0d07f1df228031014cd2351c2
libxml2: don't grow dependency on liblzma if that happens to be installed

Change-Id: Ifd46fc5dc531bd5bdb489c7550476f9c07a0a976
configure: no Xinerama on Darwin

Change-Id: Iad86269939cd75f9158f86e6da04952f85868e5a
configure: ENABLE_NPAPI_FROM_BROWSER requires Xt library

Change-Id: I023927897787ae046baf2751d0e56bfca3fb688f
libxmlsec: openssl conditional was accidentally inverted

... in commit bf6d1f77420dcc9ece4d9f4eae1e37b427d85c6a.  And it just
happens to not build with clang here.

Change-Id: Ic467abc894b9c98c81fa64cb57eafaa4cfcaa66e
configure: we need both cups header and library

Change-Id: Ie27a67b7d1086fbbce5eb40a56b4d154afb3faf8
configure: check for ICE and SM libraries too

Change-Id: Id86b09c9f2fe8770da8cc6b13672e2bf37201962