Allow building without documentation.

Allows building without documentation even if asciidoc and xmlto are
installed. This eases up working with the build system because doc
generation take quite a while on repeated builds.
Signed-off-by: Mikko Koppanen <mkoppanen@php.net>

acinclude.m4

@@ -65,26 +65,35 @@ dnl # AC_CHECK_DOC_BUILD
 dnl # Check whether to build documentation and install man-pages                 #
 dnl ##############################################################################
 AC_DEFUN([AC_CHECK_DOC_BUILD], [{
-    # Determine whether or not documentation should be built and installed.
-    build_doc="yes"
-    install_man="yes"
-    # Check for asciidoc and xmlto and don't build the docs if these are not installed.
-    AC_CHECK_PROG(have_asciidoc, asciidoc, yes, no)
-    AC_CHECK_PROG(have_xmlto, xmlto, yes, no)
-    if test "x$have_asciidoc" = "xno" -o "x$have_xmlto" = "xno"; then
+    # Allow user to disable doc build
+    AC_ARG_WITH([documentation], [AS_HELP_STRING([--without-documentation],
+        [disable documentation build even if asciidoc and xmlto are present [default=no]])])
+
+    if test "x$with_documentation" = "xno"; then
         build_doc="no"
-        # Tarballs built with 'make dist' ship with prebuilt documentation.
-        if ! test -f doc/zmq.7; then
+        install_man="no"
+    else
+        # Determine whether or not documentation should be built and installed.
+        build_doc="yes"
+        install_man="yes"
+        # Check for asciidoc and xmlto and don't build the docs if these are not installed.
+        AC_CHECK_PROG(have_asciidoc, asciidoc, yes, no)
+        AC_CHECK_PROG(have_xmlto, xmlto, yes, no)
+        if test "x$have_asciidoc" = "xno" -o "x$have_xmlto" = "xno"; then
+            build_doc="no"
+            # Tarballs built with 'make dist' ship with prebuilt documentation.
+            if ! test -f doc/zmq.7; then
+                install_man="no"
+                AC_MSG_WARN([You are building an unreleased version of 0MQ and asciidoc or xmlto are not installed.])
+                AC_MSG_WARN([Documentation will not be built and manual pages will not be installed.])
+            fi
+        fi
+
+        # Do not install man pages if on mingw
+        if test "x$on_mingw32" = "xyes"; then
             install_man="no"
-            AC_MSG_WARN([You are building an unreleased version of 0MQ and asciidoc or xmlto are not installed.])
-            AC_MSG_WARN([Documentation will not be built and manual pages will not be installed.])
         fi
     fi
-    
-    # Do not install man pages if on mingw
-    if test "x$on_mingw32" = "xyes"; then
-        install_man="no"
-    fi
 
     AC_MSG_CHECKING([whether to build documentation])
     AC_MSG_RESULT([$build_doc])