vcc_act_call() implements use-before-define semantics. To do so, it
needs to instantiate SUB symbols if they do not exist.

However, it wrongly called VCC_GlobalSymbol() also for existing
symbols, overwriting symbol properties.

In the case of the built-in subs, the symbol's lname (historically)
still is the unescaped literal name, while user defined subs have
their name escaped via VCC_GlobalSymbol() -> VCC_PrintCName().

This made the wrong call to VCC_GlobalSymbol() apparent when a
built-in sub was called with an explicit "call" action.

Besides fixing the VCC_GlobalSymbol() call, we also need to set the
lname and rname attributes for built-in SUB symbols initialized in
VCC_New().

Alternatively, we could also have used VCC_GlobalSymbol() there, but
that would have affected other places where we (still) rely on the
known name scheme of built-in subs, e.h. EmitStruct(). While the name
unifaction was nice in general, I found the necessary changes (look up
SUB symbols) not worth the benefit.

Fixes #3719