Upgrade configure version

* configure.ac: Here.

Upgrade configure version
* configure.ac: Here.
60b0e894 · Etienne Renault · 5d12e676 · 60b0e894
Commit 60b0e894 authored Jan 08, 2019 by Etienne Renault
--- a/configure.ac
+++ b/configure.ac
 ##
 ## Configure Nolimips: a MIPS emulator with unlimited registers.
 ##
-AC_PREREQ([2.59])
+ AC_PREREQ([2.63])


 ## Project -----------------------------