The original implementation of Tcl was all strings, but they improved
performance significantly by introducing typed "objects" (integers,
lists, code, etc).  It's past time we made use of that; that happened
in Tcl 8.0 which was released in 1997.

This patch also modernizes some of the error-reporting code, which may
cause small changes in the spelling of complaints about bad calls to
PL/Tcl-provided commands.

Jim Nasby and Karl Lehenbauer, reviewed by Victor Wagner