Use the default method CC in GetFullTypeForDeclarator.

Before this patch explicit template instatiations of member function templates
were failing with the microsoft abi and 32 bits. This was happening because
the expected and computed function types had different calling conventions.

This patch fixes it by considering the default calling convention in
GetFullTypeForDeclarator.

This fixes pr17973.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@195032 91177308-0d34-0410-b5e6-96231b3b80d8