Merge branch 'hotfix/0.12.1'
BUG FIX: product(x, na.rm=FALSE) for integer 'x' with missing values gave garbage
Now using storage mode "double" instead of "numeric" in all tests
productExpSumLog() no longer uses abs()/fabs().
Added 'make clang'
Now Makefile finds R_HOME on all systems
Merge branch 'hotfix/0.12.2' into develop