./configure needs to use $CRYPTLIB when checking for crypt()

./configure needs to use $CRYPTLIB when checking for crypt()

When ./configure checks for the crypt() function, it should have -lcrypt
in $LIBS (if -lcrypt was found).  Created a special AC_CHECK_FUNCS
for crypt() that temporarily adds $CRYPTLIB to $LIBS.

This became a problem when #if HAVE_CRYPT was added to
helpers/basic_auth/NCSA/ncsa_auth.c.  The crypt() function was always
there, but not always surrounded by the #ifdef.