PR21823: 'nodebug' attribute on global/static variables.

Make 'nodebug' on a global/static variable suppress all debug info
for the variable. Previously it would only suppress info for the
associated initializer function, if any.

Differential Revision: http://reviews.llvm.org/D19567


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267746 91177308-0d34-0410-b5e6-96231b3b80d8