Merge branch 'master' into InterleavedNDTwistedClover
Merge pull request #259 from kostrzewa/source_generation_seed

fixes related to online measurements and source generation
Merge remote-tracking branch 'upstream/master' into InterleavedNDTwistedClover
Merge remote-tracking branch 'origin/InterleavedNDTwistedClover' into InterleavedNDTwistedClover
add _THREAD_OVERLAP configure define which allows for more efficient overlapping with MPI when threads are available, this is NOT used when SPI is available
add some more clarifying comments for #ifdef structure due to _THREAD_OVERLAP