[Amforth] words/icompare.asm bugfix

[Enoch <ix...@ho...>]

Hello Matthias & All:

Signed comparison prevented us until now from enjoying UTF-8.
Not any more :-)

: Σ  0 swap 0  do  +  loop  ;
> 7 8 9 3 Σ .
24  ok

Patch at http://pastebin.com/seSSPUtx

Regards, Enoch.