Fixed PC speaker sound volume in PIT mode 0;
A few CPU emulation clean-ups;
Hard disk controller changing redone in a less messy way;
Re-added the long-missing key send delay handling to the XT keyboard handler;
Fixed a bug that was causing SLiRP not to work when compiled with MingW/GCC 7.3.0-2 or newer;
Some serial mouse and port fixes;
A lot of changes to printer emulation, mostly based on DOSBox-X;
Printer PNG writer now uses statically linked libpng;
Added support for the HxC MFM floppy image format and upped 86F format version to 2.12;
Ported various things from PCem and some from VARCem;
Added the S3 86c801/805 emulation (patch from TheCollector1995);
Fixed and renamed the EGA monitor options;
Better synchronized the 808x to the PIT and the CGA;
Fixed the CGA wait state calculation;
Cleaned up some things in mem.c;
Fixed some things in the floppy emulation to make VisiOn get the correct errors from the copy protection disk;
Fixed several renderer-related bugs, including the SDL2 renderer's failure to take screenshots;
The Jenkins builds are now compiled with MingW/GCC 7.4.0-1 and include all the required DLL's.
