Remove feature HAVE_QSORT

qsort conforms to C99, so we don't need our own version.
remove HAVE_SETJMP_H
remove HAVE_ERRNO
remove HAVE_BCMP
remove HAVE_MEMCMP
remove HAVE_MEMSET
remove HAVE_MATH_H
remove HAVE_INTTYPES
remove HAVE_STDINT
remove HAVE_STDARG_H
remove HAVE_{ISWUPPER,ISWLOWER,TOWUPPER,TOWLOWER}