HG revision 89 Alan Donovan
go.tools/ssa: fix crash on 'select { case x, ok = <-ch: }' (= not :=).

Added test.

Also:
- abstracted Function.addLocalForIdent (9 calls).
- remove vestige of old typeswitch hack.
- specify and fix CallCommon.Signature() for calls to built-ins.
go.tools/ssa: remove workaround for missing go/types check, now fixed.
HG changeset revision 90 from Alan Donovan
go.tools/ssa: Function.Synthetic documents provenance of synthetic functions.

We use the new field to determine whether or not a function is
synthetic, not Pos() == 0, so synthetic functions can have
positions too.

Revision 91 Alan Donovan