[m-dev.] for review: new debugger command set (part 1 of 4)

[Fergus Henderson]

> Index: trace/mercury_trace_help.h
> Index: trace/mercury_trace_help.c

These files were not mentioned anywhere in the log message,
as far as I can tell.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.