[PicForth] Installation comments

[J.C. Wren]

A couple of observations while trying to get PicForth up:

    The makefile refers to dcc2.  dcc2.fs does not exist, so the make 
aborts.
    Makefile attempts to change into the ./doc directory, which does not 
exist.
    There appears to be a missing Makefile that belongs in ./doc

    gforth picforth.fs -e 'host picquit' does indeed drop one into an 
interactive shell.  It should probably be noted for the benefit of 
inexperienced users poking around that once in the shell, you need to do 
'include myfile.fs' before the various interactive words (see, map, dis, 
words) generate any output.