Fully implement overlapped I/O for Windows serial ports.
Allow creation and selection of truly empty chart groups.
Allow minimal builds from read-only source tree.
Improve raster texture cache file management.
Correct fault in options->ships->MMSI Properties "Edit" dialog
debug
Revert "debug"

This reverts commit a31305544e4d0ca66c9b92412c7abb88d01f5225.
Correct tide/current database location validation logic to allow arbitrary path.
Merge branch 'overlap'
Correct wording of MMSI Properties option "Handle this MMSI as SART/PLB MOB." (FS#1549)
Correct broken file selection in grib dialog