Don't use termcap.c on Posix platforms, only on MS-DOS.
configure.in <AC_CHECK_HEADERS>: Remove termcap.h.
configure: Regenerated.
src/Makefilie.in (termcapobj): Move termcap.o from here...
(MSDOS_OBJ): ...to here.
(termcapobj) [!LIBS_TERMCAP]: Remove specialized value, as it is
now identical to when LIBS_TERMCAP is defined.
src/term.c: Remove (ifdef'ed away) inclusion of termcap.h.
src/cm.c: Remove (ifdef'ed away) inclusion of termcap.h.
src/config.in: Regenerated.