After a Tcl_SetObjResult, don't do a Tcl_TransferResult to the same interpreter
Stop [glob] complaining about empty list result.  Continue support for
a no-op -nocomplain option, but don't document it.  Old script support only.
Re-fix failing load-3.2 test.  The right way this time.
Remove all maintenance of a string result in the Interp.
Initialize legacyFreeProc with invalid value: This will result in
a crash immediately, when an extention tries to call it, in stead
of crashing some time later....
Remove some more legacy regarding accessing interp->result
Remove obsolete functions Tcl_GetDefaultEncodingDir and Tcl_SetDefaultEncodingDir
This branch explores the performance implications of relacing the
dynamic array data structure underlying Tcl_Preserve/Release with a
Tcl_HashTable, i.e a change from nominally O(n) to nominally O(1).  In
this initial work the Reference data structures are individually
allocated and freed. A continuation may add a free-list of structures
for quicker re-use without going through the memory manager.

Other things we can explore here: Does it make sense to use TSD (i.e.
Thread-Specific Data), to get rid of the mutex currently used in this
subsystem ? Or even better, can we assume that preserved data is
always tied to some interpreter, allowing us to tie the data
structures here in the same manner ?