re-add Windows visual studio build back into the travis-ci tests

New procedures added to win/win32/vs2017/travisci.sh for travis-ci testing.

- use curl to obtain Lua from http://www.lua.org/ftp/lua-5.3.5.tar.gz
- use tar to unzip lua into lib/lua-5.3.5/...

Note: curl and tar were both added as part of Windows 10 in late Dec 2017
   https://techcommunity.microsoft.com/t5/Containers/Tar-and-Curl-Come-to-Windows/ba-p/382409

- use git to clone pdcurses into lib/pdcurses
- use git to clone universal-ctags into lib/ctags
- build universal-ctags ahead of building NetHack + lua + pdcurses
- adjust sys/winnt/Makefile.msc to look for those things in their lib locations when
  building under travis

sys/winnt/Makefile.msc

@@ -527,7 +527,12 @@ DATABASE = $(DAT)\data.base
 # ctags options
 #
 #CTAGSCMD=ctags-orig.exe
+!IF "$(TRAVIS_BUILD_DIR)" != ""	
+CTAGSCMD=..\lib\ctags\ctags.exe
+!ELSE
 CTAGSCMD=..\..\..\ctags\ctags.exe
+!ENDIF
+
 CTAGSOPT =--language-force=c --sort=no -D"Bitfield(x,n)=unsigned x : n" --excmd=pattern
 #
 # ctags wants unix-style pathnames