fix libmach bug, visible under acid.
to reproduce the bug:

acid /bin/ls                                                                    
acid: filepc("lsxxx:1")                                                         
acid 1591: suicide: sys: trap: fault read <skipped>

Reference: /n/sources/patch/applied/libmach
Date: Sat Jan 22 16:59:04 CET 2005

--- /sys/src/libmach/sym.c	Sat Jan 22 16:59:05 2005
+++ /sys/src/libmach/sym.c	Sat Jan 22 16:59:04 2005
@@ -356,13 +356,12 @@
 			return 0;
 		}
 	}
-	fmax++;
-	fnames = malloc(fmax*sizeof(*fnames));
+	fnames = malloc((fmax+1)*sizeof(*fnames));
 	if (!fnames) {
 		werrstr("can't malloc file name table");
 		return 0;
 	}
-	memset(fnames, 0, fmax*sizeof(*fnames));
+	memset(fnames, 0, (fmax+1)*sizeof(*fnames));
 	files = malloc(nfiles*sizeof(*files));
 	if(!files) {
 		werrstr("can't malloc file table");