printf: fix printf "%u\n" +18446744073709551614

function                                             old     new   delta
conv_strtoll                                          19      32     +13
conv_strtoull                                         49      61     +12
bb_strtoll                                            89      84      -5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 25/-5)              Total: 20 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/bb_strtonum.c b/libbb/bb_strtonum.c
index cb70f10..2185017 100644
--- a/libbb/bb_strtonum.c
+++ b/libbb/bb_strtonum.c
@@ -81,7 +81,7 @@
 	/* Check for the weird "feature":
 	 * a "-" string is apparently a valid "number" for strto[u]l[l]!
 	 * It returns zero and errno is 0! :( */
-	first = (arg[0] != '-' && arg[0] != '+' ? arg[0] : arg[1]);
+	first = (arg[0] != '-' ? arg[0] : arg[1]);
 	if (!isalnum(first)) return ret_ERANGE();
 
 	errno = 0;