Patch for NDK r10 and Android-L

With the NDK r10 and Android-L, android.toolchain.cmake could not find the NDK_API_LEVEL as it was doing before.

Indeed, it was looking in the corresponding file (`api-level.h` corresponding to the platform) for:

    #define __ANDROID_API__ <version>

With <version> being a number. Now, the files look like:

    #define __ANDROID_API__ 9999 /*'L'*/

But `9999` does not work with CMake, since it is expecting `L`.

I therefore added a new regex to handle this case.