Fix invocation of closures via .call in the VM

Fix invocation of closures via .call in the VM.

Calling closures via .call does now work in the VM - it was working in
dart2js already.  Calling .call on a closure is implemented to go through
a dispatcher method. These dispatcher methods are automatically created and
cached in the same way as NoSuchMethod- or field-invocation dispatchers.

This CL does not change the way regular closure invocation works in
the VM. It is therefore performance-neutral for normal closure calls.

BUG=dartbug.com/12602
TEST=language/call_test
R=iposva@google.com

Committed: https://code.google.com/p/dart/source/detail?r=33576

[Ivan Posva, 2014-03-12 13:32:18]

LGTM -ip

[Florian Schneider, 2014-03-12 14:02:43]

Committed patchset #2 manually as r33576 (presubmit successful).