Completely reorganized the selection scheme for

   Completely reorganized the selection scheme for
   pcre, pcreposix, pcrs and gnu_regex:

   The presence of shared pcre, pcreposix or pcrs
   libraried is now autodetected. Additionally, the
   user can enforce using the built-in static variants
   by specifying --disable-dynamic-(pcre|pcrs).
   Care is taken to avoid that pcre is dyn, while pcreposix
   is static, if both are used and that pcrs is static if
   pcrs is.

   The choice between pcre, gnu or no regex for actionsfile
   URL matching is now via
   --(enable|disable)-regex-matching[=(gnu|pcre|no)] with the
   default being pcre.