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.