AX_APPEND_FLAG changed behaviour

Hello,

I noticed that in the most recent version of the archive, AX_APPEND_FLAG 
has changed behaviour and does add the FLAG also when the variable 
contains FLAG. I traced down the altered behaviour to the two lines

  [case " AS_VAR_GET(FLAGS) " in
     *" $1 "*)

which have changed to

   AS_CASE([AS_VAR_GET(FLAGS)],
     ["* $1 *|*$1"]

besides that AS_CASE is used (which is good imho) the pattern has 
changed and the space around FLAGS in the first argument of AS_CASE has 
gone. This means that e.g. if FLAGS is "alpha beta gamma" that will not 
match the pattern "* $1 *|*$1" for $1 being any of 'alpha', 'beta', or 
'gamma'. I think that is unexpected behaviour.

Easiest would be to just move back to the old pattern, but wanted to 
check if there was any reason for the modification, in which case we 
perhaps can come up with something better.

Thank,
Peter