Convert a string to upper or lower case   astChrCase 
  
" out" string are used as the input string.  " blen" . If NULL is supplied for " in" , then the supplied
                                                                                       
                                                                                       
contents of " out" are converted and written back into " out" over-writing the
supplied contents.  " in" is NULL. No more than " blen - 1" characters will be copied
from " in" to " out" , and a terminating null character will then be added.