#565 interp state audit

[Don Porter]

while working on 2823282, I noticed some
Tcl_SaveInterpState, Tcl_SaveResult,
Tcl_ResetResult, etc. calls that I could not
account for the need for, and which when
disabled did not trigger test suite failures.

A general audit to determine better where
such things are needed and where they are
not would be a good idea, along with tests
to verify their presence where they truly
are needed.