Fix Android build script on Windows 64 bit (NDK r10e)

- Correct Host OS name on Windows 64 bit in common.py
- Add the missing Host OS in toolchain file for NDK r10e
- Downgrade to LLVM 3.5 when using Windows NDK r10e,
  because the prebuilt version 3.6 is missing the llvm-ar
  utility which is needed by the build script.
diff --git a/android/scripts/common.py b/android/scripts/common.py
index 2611d9e..777d23f 100644
--- a/android/scripts/common.py
+++ b/android/scripts/common.py
@@ -211,7 +211,7 @@
 
 NDK_HOST_OS_NAMES = [
 	"windows",
-	"windows_x86-64",
+	"windows-x86_64",
 	"darwin-x86",
 	"darwin-x86_64",
 	"linux-x86",