Remove excessive padding from MismatchingNewDeleteDetector

The class MismatchingNewDeleteDetector is in 
lib/Sema/SemaExprCXX.cpp inside the anonymous namespace.
This diff reorders the fields and removes the excessive padding.
Test plan: make -j8 check-clang

Differential revision: https://reviews.llvm.org/D23898

llvm-svn: 280426