configure: pass noyywrap to AC_PROG_LEX if using autoconf 2.70 or later
Raises minimum autoconf version from 2.60 to 2.64 for m4_version_prereq
Clears autoconf warning:
configure.ac:47: warning: AC_PROG_LEX without either yywrap or noyywrap is obsolete
./lib/autoconf/programs.m4:743: _AC_PROG_LEX is expanded from...
./lib/autoconf/programs.m4:736: AC_PROG_LEX is expanded from...
configure.ac:47: the top level