xorg-server: major bump 1.14.* -> 1.16.1 (incl. deps)

(cherry picked from commit 2e4c71a070344d72392860c2f462af00d62a9d7c)
thunderbird: update to 31.2.0, including security

Some "critical security fixes" are claimed:
https://www.mozilla.org/security/known-vulnerabilities/thunderbird/#thunderbird31.2.0

(cherry picked from commit 1918f8737be29e84ea4986e1367cf3943e0c3226)
WIP: fontconfig
TEMPORARY fonts.conf fix to avoid rebuilds
fontconfig: finish and document
evince-3.12: maintenance update
gtkmm and related *mm updates
qt4: apply a patch from (K)Ubuntu

Suggested by @ruediger on IRC.
TMP: add forgotten file
mesa: fix LLVM runtime dependency (close #4853)

ToDo: test that gallium drivers still work after this.