Add the misc-init-local-variables check.

This checks finds all primitive type local variables (integers, doubles, pointers) that are declared without an initial value. Includes fixit functionality to initialize said variables with a default value. This is zero for most types and NaN for floating point types. The use of NaNs is copied from the D programming language.

Patch by Jussi Pakkanen.

llvm-svn: 373489