libx264: Remove X264_API_IMPORTS.

This is defined as needed in libx264.pc

projects:Update for recent upstream merge.

project: Split appveyor jobs by platform.

projects: Update for recent merge.

project: Modify appveyor support to remove VS 2013 and add VS 2019.

projects: Update for recent upstream merge.

projects: Update for recent upstream merge.

projects: Update for recent usptream merge.

projects: Update for recent upstream merge.

projects: Update for recent upstream merge.