test failure osx (el capitan) with valgrind 3.11.0

[redboltz]

Some tests fail on osx (el capitan) with valgrind 3.11.0.
Without valgrind, no errors are detected.
See also #524 and #525.

[redboltz]

http://stackoverflow.com/questions/40650338/valgrind-on-macos-sierra
http://stackoverflow.com/questions/34573039/possible-memory-leak-valgrind-in-osx-el-capitan
http://stackoverflow.com/questions/12452541/valgrind-reports-leaked-memory-on-os-x-10-8-1

It seems that valgrind is the tool for linux not macos basically, so valgrind checking should be removed from macos build.