Replace svn_version with default amxmodx_version which should get replaced by AMBuild regardless

plugins/include/amxmodx_version.inc

@@ -0,0 +1,16 @@
+/* AMX Mod X constants
+*
+* by the AMX Mod X Development Team
+*  originally developed by OLO
+*
+* This file is provided as is (no warranties).
+*/
+
+#if defined _amxmodx_version_included
+  #endinput
+#endif
+#define _amxmodx_version_included
+
+#define AMXX_VERSION		0
+#define AMXX_VERSION_NUM	0
+stock const AMXX_VERSION_STR[] = "AMBuild failed?";