scriptcontext and isolatecontext now allow plain text mnemonics for
context level arguments (one of CORE, CFG, PROMPT, MAPCFG, MDLCFG)
also:
- cleanup (some dead code and dead prototypes removed)
- some stuff renamed
- script errors now show context levels
- conc is no longer thread-safe (but slightly faster)
DOCREF scriptcontext isolatecontext