Candidate fix for #1305 (no test case written yet, so it isn't fixed.) Addresses #1305.

git-svn-id: file:///svn/toku/tokudb.1032b@8250 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/bread.c

@@ -43,7 +43,7 @@ ssize_t bread_backwards(BREAD br, void *vbuf, size_t nbytes) {
 	}
 	if (nbytes>0) { 
 	    assert(br->bufoff==0);
-	    size_t to_read = ((size_t)br->current_offset >= br->bufsize) ? br->bufsize : (size_t)br->current_offset;
+	    size_t to_read = ((u_int64_t)br->current_offset >= (u_int64_t)br->bufsize) ? br->bufsize : (size_t)br->current_offset;
 	    ssize_t r = pread(br->fd, br->buf, to_read, br->current_offset-to_read);
 	    assert(r==(ssize_t)to_read);
 	    br->bufoff = to_read;