Use "--trace-children=yes" option for MemCheck(valgrind) to handle
leantests shell script
Add script for using HPC cluster

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
Turn off '--show-reachable=yes' valgrind option
Update .travis files to continue memcheck if it generates exceptions
Use "--leak-check=full" option in valgrind
Fix memory leaks in mpfp.h
Fix initialized memory error reported by Valgrind. Disable 2 tests that produce memory leaks due to a bug in g++.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>