Apply patches for LLVM 3.9

Patches 1 and 2 fix a bug (that has been present in 3.7 and 3.8)
where it can use the wrong instruction in some cases (libav
with inline assembly disabled), causing rounding errors in
integer audio dct's there.

Patch 3 allows building inline assembly with clang/llvm in MSVC mode.

Dockerfile

@@ -26,6 +26,9 @@ RUN cd llvm/tools && \
 #    git clone -b release_38 --depth=1 https://github.com/llvm-mirror/libcxxabi.git && \
 #    git clone https://github.com/llvm-mirror/libunwind.git -b release_38 --depth=1
 
+RUN cd llvm && \
+    git am /build/patches/llvm-*.patch
+
 RUN cd llvm/tools/clang && \
     git am /build/patches/clang-*.patch