Initial check-in with these changes from the forked library:

• Several adoptions for std::string and compiler error fixes for Android & iOS.
• Fix for reading local files.
• Fix for reading samples from file.
• Adds std:: to stl types (#061)
• Fix memory leak caused by calling MP4Modify(). This is caused by a “free” atom getting removed without de-allocating.
• Fix rounding issue in mp4util.cpp.
• Support reading mp4 container structure from file offset.
• Fix offset handling.
• Add CAMM atom to mp4v2.
• Create MP4 with CAMM and video using mp4v2.
• Add an MP4FileProvider that uses URLProtocol to do IO to the MediaDecoder class.
• Add instructions for environment variable setup for mp4v2 muxer.
• Supports muxing a list of frames.
• Changes the type of lat/lng/altitude in case 5 from float to double.
• Adds MP4_CREATE_64BIT_DATA to MP4Create, so that it can handle large files.
• Fix calls to std::string::operator=.