AC_CHECK_LIB, and AC_CHECK_FUNCS. Change AC_OUTPUT to set
stamp-h.
* configure: Rebuild.
* config.in: New file, generated by autoheader.
* interp.c: Include "config.h". Include <stdlib.h>, <string.h>,
and <strings.h> if they exist. Replace #ifdef sun with #ifdef
HAVE_ANINT and HAVE_AINT, as appropriate.
* Makefile.in (run): Use @LIBS@ rather than -lm.
(interp.o): Depend upon config.h.
(Makefile): Just rebuild Makefile.
(clean): Remove stamp-h.
(mostlyclean): Make the same as clean, not as distclean.
(config.h, stamp-h): New targets.
