even more improved way to find the necessary include path

ax_init_standard_project.m4

@@ -418,7 +418,15 @@ AC_DEFUN([AX_PKG_REQUIRE], [
     CPPFLAGS=${old_CPPFLAGS}
   fi
   if test ${$1_found} -eq 0; then
-    AC_MSG_ERROR([Feature $1 not found, need header $3 in module $2 $4])
+    if test -n "$3"; then
+      if test -n "$4"; then
+        AC_MSG_ERROR([Feature $1 not found, need header $3 in modules $2 or $4])
+      else
+        AC_MSG_ERROR([Feature $1 not found, need header $3 in module $2])
+      fi
+    else
+      AC_MSG_ERROR([Feature $1 not found please install module $2])
+    fi
   fi
   AM_CPPFLAGS+=" ${$1_CFLAGS}"
   AM_CXXFLAGS+=" ${$1_CFLAGS}"