Slightly change the help text for some options that involve
user-supplied enumeration values.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14447 a5019735-40e9-0310-863c-91ae7b9d1cf9
Document the new --kernel-variant options committed in r14440.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14448 a5019735-40e9-0310-863c-91ae7b9d1cf9