Makes the build system to look for yajl using a macro file

Now searching for yajl using find_yajl.m4 macro file instead
of using pkg-config directly. If YAJL was not found or if it
was disabled in the configure phase, the code will be compiled
without JSON support.

apache2/msc_json.h

@@ -14,11 +14,19 @@
 
 #ifndef _MSC_JSON_H_
 #define _MSC_JSON_H_
+#ifdef WITH_YAJL
 
 typedef struct json_data json_data;
 
+
 #include "modsecurity.h"
+
 #include <yajl/yajl_parse.h>
+//#ifdef WITH_YAJL
+//#else
+
+
+#include "modsecurity.h"
 
 /* Structures */
 struct json_data {
@@ -46,3 +54,4 @@ int DSOLOCAL json_complete(modsec_rec *msr, char **error_msg);
 apr_status_t DSOLOCAL json_cleanup(modsec_rec *msr);
 
 #endif
+#endif