[DebugCounter] Move the semicolon out of the DEBUG_COUNTER macro and require...

[DebugCounter] Move the semicolon out of the DEBUG_COUNTER macro and require it to be placed at the end of each use.

This make it consistent with STATISTIC which it will often appears near.

While there move one DEBUG_COUNTER instance out of an anonymous namespace. It's already declaring a static variable so the namespace is unnecessary.

llvm-svn: 310637