HR fix of #236636 - NullPointerException at com.sun.tools.javac.comp.Attr.attribTypeVariables

https://netbeans.org/bugzilla/show_bug.cgi?id=236636

Problem: While entering type parameters of a class, duplicated type 
parameters are detected and the corresponding error message is being 
prepared. However, to prepare the correct error message, flags of the 
class have to be checked that initiates completion of the corresponding 
ClassSymbol with MemberEnter as the completer. Thus MemberEnter is run 
on the ClassSymbol with unfinished Enter phase.

Fix: Set ClassSymbol's completer to MemberEnter after the class type 
parameters are processed by Enter.

http://hg.netbeans.org/main/nb-javac/diff/3d13b661be63/src/share/classes/com/sun/tools/javac/comp/Enter.java

Thanks,
Dusan