Inappropriate InitializationStyle

Hi Sebastian,

in r150318 you've finally introduced the most needed InitalizationStyle,
but in

struct S {
  S();
};

S x;

for the last VarDecl, the InitStyle is set to CallInit, but this is not
truly appropriate.
What do you think about introducing another style called NoInit to be
used in cases where there is no written initializer?

It would improve the source fidelity. I'm not sure if it would make the Clang source code better.

Sebastian