Add some short delays between input and output phases or processing s…

…o that messages can be udated, and the browser can respond to the user (in case multiple typeset calls are queued simultaneously). Resolves issue mathjax#872.

unpacked/MathJax.js

@@ -1902,6 +1902,7 @@ MathJax.Hub = {
   inputJax: {},          // mime-type mapped to input jax (by registration)
   outputJax: {order:{}}, // mime-type mapped to output jax list (by registration)
 
+  processSectionDelay: 50, // pause between input and output phases of processing
   processUpdateTime: 250, // time between screen updates when processing math (milliseconds)
   processUpdateDelay: 10, // pause between screen updates to allow other processing (milliseconds)
 
@@ -2058,11 +2059,15 @@ MathJax.Hub = {
         ["Post",this.signal,["Begin Math Input",elements,action]],
         ["processInput",this,state],
         ["Post",this.signal,["End Math Input",elements,action]],
+        ["Delay",MathJax.Callback,this.processSectionDelay],
         ["prepareOutput",this,state,"preProcess"],
+        ["Delay",MathJax.Callback,this.processSectionDelay],
         ["Post",this.signal,["Begin Math Output",elements,action]],
         ["processOutput",this,state],
         ["Post",this.signal,["End Math Output",elements,action]],
+        ["Delay",MathJax.Callback,this.processSectionDelay],
         ["prepareOutput",this,state,"postProcess"],
+        ["Delay",MathJax.Callback,this.processSectionDelay],
         ["Post",this.signal,["End Math",elements,action]],
         ["Post",this.signal,["End "+action,elements]]
       );