Too much synchronization in JXPathIntrospector

The class JXPathIntrospector has been refactored lately to use Collections.synchronizedMap for the static [byClass] and [byInterface] maps, however access to them in code is still synchronized, while I believe it should be not since the synchronized-map methods are already locked on the instance and only one operation is involved.

I propose to remove the synchronized keyword from the following blocks:

https://github.com/apache/commons-jxpath/blob/trunk/src/java/org/apache/commons/jxpath/JXPathIntrospector.java#L71

https://github.com/apache/commons-jxpath/blob/trunk/src/java/org/apache/commons/jxpath/JXPathIntrospector.java#L89

https://github.com/apache/commons-jxpath/blob/trunk/src/java/org/apache/commons/jxpath/JXPathIntrospector.java#L94

https://github.com/apache/commons-jxpath/blob/trunk/src/java/org/apache/commons/jxpath/JXPathIntrospector.java#L125

I also dont' see any reason why findInformant() should be synchronized and propose to make it not synchronized. Current code does not use any static field so is safe to change and does not prevent creation of duplicate JXPathBeanInfo instances that however I believe is not relevant.

https://github.com/apache/commons-jxpath/blob/trunk/src/java/org/apache/commons/jxpath/JXPathIntrospector.java#L177