commence deprecation
Update src/Makevars.win to GEOS 3.10.2 for R < 4.2
fix -Wstrict-prototypes problems
adapt to OverlayNG in GEOS 3.9
update Windows static library to GEOS 3.9
add gMinumumRotatedRectangle() and gMaximumInscribedCircle() for GEOS 3.9
adapt configure.ac for GEOS 3.10
add support for structured geometry fixer in gMakeValid() from 3.10
add gMakeValid() for GEOS 3.8
update Windows static library to GEOS 3.8
add gCoverageUnion()
add stdlib.h to configure.ac