[Swan-dev] strip_prefix + enum_show + bitnamesof

[D. Hugh Redelmeier]

| From: Andrew Cagney <andrew.cagney at gmail.com>

| then I can display a truncated value vis:
| 
|    strip_prefix("ESN_", enum_enum_show(ikev2_trans_type_esn_names,
| IKEv2_ESN_DISABLED))
|    -> "DISABLED"

It seems that strip_prefix is used about 45 times.  That's often
enough to be catered to.

Idea: introduce

1) a "prefix" field into struct enum names

2) add new functions "enum_showb_short" and "enum_name_short" that
   suppress the prefix found in struct enum names
   Don't bother with a version of enum_show: let's not make
   another function with confusing storage for the result

3) we could add a shortbitnames function.  That would take an extra
   argument, prefix-to-be-suppressed.  (There is no descriptor struct
   to contain the prefix.  I guess we could add one.)

Is that reasonable?