Apply "exactly fill up the buffer" fix from toybox's bunzip.c.

Quoting the original commit message:

> It's not a problem to exactly fill up the buffer with a run if the
> next symbol is the terminating symbol. Fixes
> https://jira.cyanogenmod.org/browse/CYAN-1896

See: http://landley.net/hg/toybox/rev/7b6fbc0475d8

lib/Bzip2.js

@@ -335,7 +335,7 @@ Bunzip.prototype._get_next_block = function() {
        literal used is the one at the head of the mtfSymbol array.) */
     if (runPos){
       runPos = 0;
-      if (dbufCount + t >= this.dbufSize) { _throw(Err.DATA_ERROR); }
+      if (dbufCount + t > this.dbufSize) { _throw(Err.DATA_ERROR); }
       uc = symToByte[mtfSymbol[0]];
       byteCount[uc] += t;
       while (t--)