[9fans] sort -df vs. μ

[erik quanstrom <quanstro@quanstro.net>]

i've been fighting a bit with the manual, and found that μlawdec(1)
was coming in the middle of the ells.  it appears that sort -df is
wrong.  we should not treat mapto[255] like sign extension.

/n/atom/plan9/sys/src/cmd/sort.c:1292,1298 - sort.c:1292,1298
  		/*
  		 * for characters out of range,
  		 * the table does not do Rflag.
- 		 * ignore is based on mapto[255]
+ 		 * ignore is computed directly.
  		 */
  		if(c != 0 && c < nelem(f->mapto)) {
  			c = f->mapto[c];
/n/atom/plan9/sys/src/cmd/sort.c:1299,1305 - sort.c:1299,1305
  			if(c == 0)
  				continue;
  		} else {
- 			if(f->mapto[nelem(f->mapto)-1] == 0)
+ 			if(f->flags & Iflag)
  				continue;
  			/*
  			 * consider building maps as necessary


this seems too obvious, so have i missed anything?

- erik