uCON64 Code (SVN)

- Disabled warnings added in newer GCC versions that are unwanted at this time
or have shockingly broken diagnostic code resulting in spurious warnings. For
uCON64 code disabled:
-Wimplicit-fallthrough
-Wformat-truncation
-Wstringop-overflow
For libdiscmage disabled:
-Wimplicit-fallthrough
-Wstringop-overflow
The unfortunate side-effect is that for older GCC versions a warning or error
will result in 3 or 2 extra lines stating that the options are not recognized.
Thanks to Philipp Seiler for pointing me to build logs at opensuse.org.

- Fixed warning about (correctly) passing 0 as size to memset() for certain
(newer?) GCC versions.
- Fixed drop_privileges() to truly drop all privileges (saved UID and GID)
when called after drop_privileges_temp().

- Fixed bug I introduced in n64_chksum(). This time for real.

- Fixed bug I introduced in n64_chksum().

- Fixed DJGPP specific issue in mem_hexdump().

- Removed extra newline after calling dm_nfo().

- 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.