Remove files generated by lex and yacc.

These will be regenerated by the build.  Furthermore, the original lev_lex.c
is not compatible with either Linux or OS X.
Ignore files generated by the Unix makefiles.
Rename getdate to get_date and fix Y2K.

OS X has its own getdate and renaming the function removes a conflict.  From
some of the headers, it seems that other systems have this conflict also.
Define appropriate symbols for Linux and OS X.
Move #include <signal.h> outside dosuspend.

Placing the include inside the function causes syntax errors on OS X.
Make -lncurses the default TERMLIB setting.

Both OS X and Linux use ncurses.
Rename termcap.h to termcaps.h.

A needed system header is also named termcap.h.
Correct for renaming of termcap.h.
Declare functions via their headers.
Include termcap.h to declare termcap functions.
Name the final binary nethack30.