Expose cxx constructor and method properties through libclang and python bindings.

Summary:
I have exposed the following function through libclang and the clang.cindex python bindings:

clang_CXXConstructor_isConvertingConstructor,
clang_CXXConstructor_isCopyConstructor,
clang_CXXConstructor_isDefaultConstructor,
clang_CXXConstructor_isMoveConstructor,
clang_CXXMethod_isDefaulted

I need (some of) these methods for a C++ code model I am building in Python to drive a code generator.

Reviewers: compnerd, skalinichev

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D15469

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267706 91177308-0d34-0410-b5e6-96231b3b80d8