Remove JQ_DEBUG #define and jq_test binary, simplifying build.

The debugging features previously available via JQ_DEBUG are now
command-line options.

jv_alloc.c

@@ -27,7 +27,7 @@ void* jv_mem_realloc(void* p, size_t sz) {
   return p;
 }
 
-#if JQ_DEBUG
+#ifndef NDEBUG
 volatile char jv_mem_uninitialised;
 __attribute__((constructor)) void jv_mem_uninit_setup(){
   char* p = malloc(1);