sweep up -Wformat warnings from gcc

This is a purely mechanical change explicitly casting any parameters for printf
style conversion.  This cleans up the warnings emitted by gcc 4.8 on Linux.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@205607 91177308-0d34-0410-b5e6-96231b3b80d8