init the spatial last spatial picture if excption
Squashed merge from writenal_refactor2
Merge pull request #325 from sijchen/writenal_refactor3

add encoder error code and refactor WelsWriteNal
remove quality layer configuration. It is not supported
Merge pull request #332 from volvet/remove-q-layer-config

remove quality layer configuration. It is not supported
Initial Commit
refine checks in ParseSps
Add ios support for dec
Initial Commit
remove cgs/mgs related code, it is not supported
Add ios support for encoder.
Initial Commit
Add ios support for common
Initial Commit
Add .gitignore to iOS folder
Remove processing ios build
Add ios build for processing
Add decoder ios demo
Modify copyright for some files
Remove the WELSAPI definition

There's no need to specify a custom calling convention for
these functions.