Fix a few undefined behaviours that were found by compiling valgrind
with GCC 4.9.2 using -fsanitize=undefined and running the testsuite.


git-svn-id: svn://svn.valgrind.org/vex/trunk@3099 8f6e269a-dfd6-0310-a8e1-e2731360e62c
9 files changed