Second v0.9 Preview Snapshot for macOS

This is a temporary preview build of Mapper 0.9 for macOS. (Builds for Windows and Linux are continuously available as "unstable" downloads.)

Key changes since v0.8:

• Qt 5.9.
• New OCD export (version 8-12, including georeferencing).
• Experimental support for OCD 2018 import.
• New geospatial vector data export.

Key changes since the first preview:

• Fixes the OCD9/10 export bug.
• Adds OCD symbol icon support.
• Adds support for offsets at line start/end.
• Includes the fixes for crashes from v0.8.3.

All changes

OpenOrienteering/superbuild@76c1b37,
cmake options:
-DCMAKE_BUILD_TYPE=Release -DUSE_SYSTEM_LIBPNG=0 -DUSE_SYSTEM_QT=0 -DMapper_GIT_TAGS=6e288c3
make target:
openorienteering-mapper-git-6e288c3-package