Handle non-inlined clang::Type::getAs specializations in extract_symbols.py
Handle non-inlined clang::Type::getAs specializations in extract_symbols.py

The existing logic was to discard any symbols representing function template
instantiations, as the definitions were assumed to be inline. But there are
three explicit specializations of clang::Type::getAs that are only defined in
Clang's lib/AST/Type.cpp, and at least the plugin used by the LibreOffice build
(https://wiki.documentfoundation.org/Development/Clang_plugins) uses those
functions.

Differential Revision: https://reviews.llvm.org/D26455

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@286841 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm