Minor bugfix release

• added the possibility to pause the threadpool
• extending CMake module path even if embedding
• fixed RPL parsing problem
• fixed buffer sizes for SEI reading
• added sanity checks for syntax element ranges
• fix for dtrace usage with vvdec namespace
• sanity checks for empty NAL units

• all VTM-12.0 Main10-profile conformance bitstreams supported (as of 12.3.2021)
• changed the external interface (libvvdec) to pure C
• general maintenance and bugfixes
• added an option to upscale the YUV output to the signaled maximal possible resolution (--upscale/-uo 2)
• added support for sub-pictures including nested SEIs
• improved GDR support
• cleanups to picture list management
• proper encapsulation of SIMD for other architectures
• improved exception handling
• fixed multiple and concurrent initialization problem
• added vvdec namespace to all internal classes
• added support for github actions

• fixes for conformance tests (cropping window, ALF, long term reference pictures, virtual boundary, WPP)
• added pkgconfig info
• fixes for non-420 chroma formats, most notably 422
• fixes for picture output problem (issues #17)
• restructured reference picture list parsing
• cleanup of CMake files
• moved conformance tests definitions out of the main CMakeLists.txt
• fixes for memory leaks, address sanitizer problems
• removal of obsolete code
• various fixes

• fixes for compilation GCC-10

• changed license (to modified BSD)
• extended the set of supported and tested test-cases (from JVET conformance set)
• fixes syntax for multiple slices
• fixes syntax for DPH-SEI
• memory reductions

• fixed outstanding issues
• fixed handling of multiple slices
• fixed handling of multiple tiles
• added additional test-cases (failing test-cases are commented-out)
• fixed conformance testcases handling
• cleanup of CABACReader
• cleanup of VLCReader
• started localizing CTU data (CtuData structure)
• changed the semantics of --threads and --parsedelay (previously parsethreads) parameters

Initial release of the work-in-progress on an optimized VVC decoder