CACHE
Enable caching support.  It is required for the CacheMaxFilesize,
CacheRProxyExtension, CacheSize settings.  CacheRProxyExtension
requires that RPROXY is also enabled.  With this option enabled
Hiawatha can cache the output of CGI applications, which can control
caching with the X-Hiawatha-Cache and X-Hiawatha-Cache-Remove
headers.

CGIWRAPPER
Install cgi-wrapper(1), which can be used to run certain CGI programs
with a different user than the webserver's user.  To function
properly, the CGI wrapper binary needs to have the setuid bit set.

LEFH
Install the 'lefh' (Let's Encrypt For Hiawatha) tool to help in
obtaining and maintaining Let's Encrypt certificates.  It requires
PHP.

LOADCHECK
Enable experimental support for MaxServerLoad.  When the host has
a load higher than that value, Hiawatha will drop incoming connections.
Officially this feature is only available on Linux.  FreeBSD support
is largely untested.

MONITOR
Enable Hiawatha Monitor support.  The MonitorServer setting enables
logging of statistical information to a remote monitor server running
www/hiawatha-monitor.  CGI scripts can log additional events via
the X-Hiawatha-Monitor header.

RPROXY
Enable reverse proxy support.  It is required for the CacheRProxyExtension,
CustomHeaderBackend, and ReverseProxy settings.  CacheRProxyExtension
requires that CACHE is also enabled.  ReverseProxy can be used to
forward requests with URLs that match POSIX regular expressions to
other webserver

TOMAHAWK
Enable support for the Tomahawk command shell.  It is exposed via
a Telnet service and can be used to view server statistics, to
ban/unban clients, to clear the cache, etc.

TOOLKIT
Enable URL toolkit support, a DSL to do URL transformations.  It
is required for the UseToolkit settings and UrlToolkit directives.
 
XSLT
With this option enabled, Hiawatha can do XSL transformation via
textproc/libxslt when an XML file is requested and an XSLT sheet
is present.  It is required for the ErrorXSLTfile, UseXSLT settings,
and XSLT support in ShowIndex.