chore(scrips): add demangle_cpptype.py
chore(travis): use demangle_cpptype.py to print out test/valgrind output

[skip ci]
test(buffer): add missing tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(hash): add missing tests

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
test(safe_arith): add unit tests

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