For usages of assert() that are meant to persist in Release builds (when NDEBUG is defined), replace those usages with persistent alternatives

src/content_cao.cpp

@@ -1718,10 +1718,12 @@ void GenericCAO::processMessage(const std::string &data)
 	}
 }
 	
+/* \pre punchitem != NULL
+ */
 bool GenericCAO::directReportPunch(v3f dir, const ItemStack *punchitem,
 		float time_from_last_punch)
 {
-	assert(punchitem);
+	assert(punchitem);	// pre-condition
 	const ToolCapabilities *toolcap =
 			&punchitem->getToolCapabilities(m_gamedef->idef());
 	PunchDamageResult result = getPunchDamage(