This resolver resolves call expressions with given function name.
It is used at least in constant resolving ( "define" can be used as
name of function , in this case resolver finds all "define" calls
and one could check its argument for constant name check ).
This resolver is responsible ONLY for simple variable resolving.
Complex variables like $a{$b} are not resolvable at all.
( we can resolve $b but this is already other variable inside complex "$a{$b}"
variable ).
Variables that are static class attributes are resolved via resolver that is
used for ClassMemberReferenceImpl.