README.commands.itest

A slow day today so here is a revised itest command with provisional
support for comparing strings as well :-))

Now table driven to allow the operators
-eq, -ne, -lt, -gt, -le, -ge, ==, !=, <>, <, >, <=, >=

Uses the expected command modifier for integer compares of width 1, 2 or
4 bytes of .b, .w, .l and the new modifer of .s for a string compare.
String comparison is over the length of the shorter, this hopefully
avoids missing terminators when using an indirect pointer.

eg.
if itest.l *40000 == 12345678 then; ....
if itest.w *40000 != 1234 then; ....
if itest.b *40000 >= 12 then; ....
if itest.s *40000 -eq hello then; ....