interactive.print_env passes ctor names as varname

[Matt Giuca]

The interactive.print_env predicate wraps all globals and ctors in gvname() and passes them to executor.show_var. Constructor names should never be in gvname(); code doesn't normally expect this to work.

It does work for interpret.show_var (since the interpret similarly places ctor names in gvname(), but that isn't a major problem because it's self-contained within that module), but it won't necessarily work for other backends.

Add a separate executor function executor.show_ctor which shows ctors without evaluating thunks (if the backend uses thunks for constructors).

[Matt Giuca (mgiuca)]

As of trunk r1178, the executor interface has been refactored and it now passes strings to executor.show_global (without wrapping in gvname). This has the same problem though -- globals are indistinguishable from ctors.

[Matt Giuca (mgiuca)]

Fixed in trunk r1179.