Two more instances of unhardcoding the project name

src/main.cpp

@@ -1153,7 +1153,7 @@ int main(int argc, char *argv[])
 	BEGIN_DEBUG_EXCEPTION_HANDLER
 
 	// Print startup message
-	dstream<<DTIME<<"minetest-c55"
+	dstream<<DTIME<<PROJECT_NAME <<
 			" with SER_FMT_VER_HIGHEST="<<(int)SER_FMT_VER_HIGHEST
 			<<", "<<BUILD_INFO
 			<<std::endl;

src/servermain.cpp

@@ -162,7 +162,7 @@ int main(int argc, char *argv[])
 	BEGIN_DEBUG_EXCEPTION_HANDLER
 
 	// Print startup message
-	dstream<<DTIME<<"minetest-c55"
+	dstream<<DTIME<<PROJECT_NAME <<
 			" with SER_FMT_VER_HIGHEST="<<(int)SER_FMT_VER_HIGHEST
 			<<", "<<BUILD_INFO
 			<<std::endl;