Simplify and refactor the uninitialized field warning.

Simplify and refactor the uninitialized field warning.

Change the uninitialized field warnings so that field initializers are checked
inside the constructor.  Previously, in class initializers were checked
separately.  Running one set of checks also simplifies the logic for preventing
duplicate warnings.  Added new checks to warn when an uninitialized field is
used in base class initialization.  Also fixed misspelling of uninitialized
and moved all code for this warning together.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193386 91177308-0d34-0410-b5e6-96231b3b80d8