Add layout for IHttpd.

--- httpd-2.4.20/config.layout.orig
+++ httpd-2.4.20/config.layout
@@ -33,6 +33,30 @@
     proxycachedir: ${localstatedir}/proxy
 </Layout>
 
+#   IHttpd layout
+<Layout IHttpd>
+    prefix:        /usr
+    exec_prefix:   ${prefix}
+    bindir:        ${prefix}/bin
+    sbindir:       ${prefix}/sbin
+    libdir:        ${prefix}/lib
+    libexecdir:    ${prefix}/libexec
+    mandir:        ${prefix}/man
+    sysconfdir:    /etc
+    datadir:       ${prefix}/share/ihttpd
+    installbuilddir: ${libdir}/ihttpd/build
+    errordir:      ${datadir}/error
+    iconsdir:      ${datadir}/icons
+    htdocsdir:     /var/www/html
+    manualdir:     ${datadir}/manual
+    cgidir:        /var/www/cgi-bin
+    includedir:    ${prefix}/include/ihttpd
+    localstatedir: /var
+    runtimedir:    /run/ihttpd
+    logfiledir:    ${localstatedir}/log/ihttpd
+    proxycachedir: ${localstatedir}/cache/ihttpd/proxy
+</Layout>     
+
 #   GNU standards conforming path layout.
 #   See FSF's GNU project `make-stds' document for details.
 <Layout GNU>