The new boolean member multi_pv of struct func_symbol represents whether
multi-pv arguments are allowed by default, i.e with -p in effect. The code
generator takes this into account when deciding what to do for a multi-PV
argument. The behaviour is now exactly as described in the release notes.

This tests rejection and warnings about bad applications of type operators.

This (large) patch also makes related changes to a number of identifiers.