Merge branch 'master' into logg/topic-multimesh

Conflicts:
	dolfin/fem/Assembler.cpp
	dolfin/fem/UFC.cpp
	dolfin/function/Function.cpp
Merge branch 'logg/topic-multimesh' of bitbucket.org:fenics-project/dolfin into logg/topic-multimesh

Conflicts:
	dolfin/function/Function.cpp
Small fixes to get code to compile with clang