curl/packages/DOS

Gisle Vanem made curl build fine on DOS (and MingW) with djgpp, OpenSSL and his
Watt-32 stack.

'make -f Makefile.dist djgpp' in the root curl dir should build it fine.
Or enter 'lib' and do a 'make -f Makefile.dj clean all' to first delete
'lib/curl_config.h' which is possibly from a previous incompatible Windows-build.

Note 1: djgpp 2.04 beta has a sscanf() bug so the URL parsing isn't
done properly. Use djgpp 2.03 until they fix it.

Note 2: Compile Watt-32 (and OpenSSL) with the same version of djgpp.
Otherwise things go wrong because things like FS-extensions and
errnos have been changed between releases.

Note 3: Several 'USE_x' variables in 'common.dj' are on the 'USE_x ?= 0'
form (conditional variable assignment). So one can build like this:
c:\curl\lib> make -f makefile.dj USE_OPENSSL=1 USE_ZLIB=1 clean all