uCON64 Code (SVN)

- Fixed buffer overflow in discmage (caused crash on DOS on low memory
systems).
- Fixed use-after-free bug in discmage.
- It is Supercom PRO and Professor SF 2.

- Made some small improvements to the Makefiles.

- Simplified discmage's Makefile by using GCC instead of LD directly. This
applies only to MinGW and Cygwin. The resulting DLLs are somewhat larger
though.

- Fixed warning when compiling with Visual Studio Community 2019 version 16.3.5.

- Corrected comment.

- Third time's the charm. Visual Studio Community 2019's /analyze is just
wrong again, but I fell for it. fname cannot be null at line 127 if the call
to malloc() on line 87 fails. Regardless malloc() failing is now fatal.
- Changed references to "Super Com Pro" into "Supercom PRO".
- Addressed issue indicated when compiling with CFLAGS=-D_FORTIFY_SOURCE=2
after configuring with --without-zlib. Added fread_checked() and
fread_checked2().
- Replaced some calls to {f}printf() with calls to {f}puts().
- Used ZLIB_VERSION instead of the ZLIB_VER_* constants in order to support
old zlib versions (like on OpenBSD).
- Added proper handling of the case when the second argument of realpath() is
null.

- Fixed linking (\!) issue on macOS (no sched_setscheduler()).

- Fix linking (\!) issue on macOS (no sched_setscheduler()).

- Same issue, but actually addressed.

- Fixed error when not using zlib.
- Fixed issue found by Visual Studio Community 2019's /analyze.