Fix make distcheck without enabled docs

Makefile.am

@@ -1,6 +1,14 @@
 # got some hints from https://gitorious.org/openismus-playground/examplelib/source
 
-SUBDIRS = po include src tools $(LIBPSL_DOCS) fuzz tests
+SUBDIRS = po include src tools
+if ENABLE_GTK_DOC
+  SUBDIRS += docs/libpsl
+else
+if ENABLE_MAN
+  SUBDIRS += docs/libpsl
+endif
+endif
+SUBDIRS += fuzz tests
 
 ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
 

configure.ac

@@ -46,7 +46,6 @@ AM_CONDITIONAL([GTK_DOC_USE_LIBTOOL], false)
 ])
 
 if test x"$have_gtk_doc" = xyes -a x"$enable_gtk_doc" = xyes; then
-  AC_CONFIG_FILES([docs/libpsl/Makefile docs/libpsl/version.xml])
   AC_SUBST([LIBPSL_DOCS], [docs/libpsl])
 fi
 
@@ -321,6 +320,7 @@ AC_CONFIG_FILES([Makefile
                  po/Makefile.in
                  fuzz/Makefile
                  tests/Makefile
+                 docs/libpsl/Makefile docs/libpsl/version.xml
                  libpsl.pc:libpsl.pc.in])
 AC_OUTPUT