After #3382 changed the escape analysis to model qualifiers as escaping,
there was an imbalance in the SSA library, where `addressTakenVariable`
excludes variables from SSA analysis if they have their address taken
but are _not_ passed by reference. This showed up as a missing result in
`TOCTOUFilesystemRace.ql`, demonstrated with a test case in #3432.
This commit changes the definition of "pass by reference" to include
call qualifiers, which allows SSA modeling of variables that have member
function calls on them.