Fix docs.

doc/ext_jit.html

@@ -151,7 +151,7 @@ Contains the target OS name:
 <h3 id="jit_arch"><tt>jit.arch</tt></h3>
 <p>
 Contains the target architecture name:
-"x86", "x64" or "ppcspe".
+"x86", "x64", "arm", "ppc", "ppcspe", or "mips".
 </p>
 
 <h2 id="jit_opt"><tt>jit.opt.*</tt> &mdash; JIT compiler optimization control</h2>