Improvement of error message in case of ambiguous call

[manuelmessner]

Condition:

type
  Foo = object
    bar: int

proc bar(cur: Foo, val: int) =
  discard cur.bar

proc does_fail(): Foo =
  result.bar(5)

can_fail()

This results in the following error message:

Error: in expression 'result.bar(5)': identifier expected, but found 'result.bar'

This error message needs some improvement, because it does not state, that the actual problem is, that there's an ambiguous call to bar.
The compiler cannot know whether the member bar of Foo is wanted, or whether the function bar should be called with result (of type Foo) as first argument.

[bung87]

fixed in 07b6453, should close.