* Tagging conditional statements

All conditional statements that match against a pattern can be tagged
using the following option:

   -tag "T"

where T is an arbitrary string.  This tag can then be used to refer to
a subexpression obtained as a result of matching, for example:

   Path -tag "dir" -re "^/static(/.*)"
   Header -tag "type" "Content-Type:([^/]+)/([^;]+)"
   SetPath "/assets/$1(type).$2(type)$1(dir)"

* Changes to the "ACL" statements

Two new forms of the ACL statements are provided:

 - ACL -file "NAME"

   Reads ACL from the file NAME.  The file shall contain a list of
   CIDRs, one per input line.  CIDRs need not be quoted.  Empty lines
   and comments are allowed.

   The file is read once, at program startup.

 - ACL -filewatch "NAME"

   Same as above, but the file will be monitored for changes during
   the runtime.  If a change is detected, the file will be rescanned
   and the ACL updated.  To ensure file changes are noticed
   immediately, pound relies on filesystem monitoring API provided by
   the operating system - inotify on GNU/Linux systems and kqueue on
   BSD.  On systems not supporting either interface, the file will be
   checked periodically.  The interval between two successive checks is
   defined by the WatcherTTL global directive.

The corresponding new forms are implemented for all ACL statements,
i.e.:

 - Named ACLs:

   ACL "name" -file "filename"
   ACL "name" -filewatch "filename"

 - Trusted IP lists:

   TrustedIP -file "filename"
   TrustedIP -filewatch "filename"

* Use of "-filewatch" with request matching directives

In addition to ACL, the -filewatch flag discussed above can be used with
the following request matching directives: Header, Path, Query, QueryParam,
StringMatch, URL.

* Changes to the "BasicAuth" statement

The statement takes an option: -filewatch or -file.  The option
-filewatch is the default (see above).  The -file option can be used
to disable file change monitoring.

* Changes to the "Header" statement

New statement form is introduced:

    Header "FIELD" [OPTIONS] "VALUE"

In this form, pattern modification options apply to header value only,
e.g.

    Header "Content-Type" -beg "text/"

* New special backend "SendFile"

This backend treats the path part of the request as local file name
and sends back the contents of that file, if it exists.  Default
content type is "text/plain".  Both parameters can be changed using
request (for file name), and response (for content type) rewriting.

The syntax is:

	 SendFile DIR

where DIR specifies the directory from which to serve files.

* Error file contents

Error file supplied with "Error", "ErrorFile", or any "ErrNNN"
directvie, can begin with HTTP headers.  If so, these will be
sent along with the response, and the actual response contents will
begin after the empty line that terminates the headers.

* Error response rewriting

  When a regular backend responds with an error, the content (body)
of that response can be replaced with an arbitrary custom page.  For
this to work, the listener must define a custom page for the
status code in question using the ErrorFile statement, and error
response rewriting must be explicitly enabled.  The latter is done
with the following statement:

   RewriteErrors on

The statement can be used both in ListenHTTP (ListenHTTPS) and in
Service blocks, the latter overriding the former.

* Bugfixes

** Improper pattern handling in patterns read from file

When using -file with one of the following pattern types: -exact, -beg,
-end, -contain, only first pattern from the file was compiled using the
requested pattern type.  Remaining ones were treated as POSIX regular
expressions.