tools: try to parse float values better

First try to parse the float value as a JSON number and then fall
back to atof to get the locale dependent variant.

This transparently makes things work with values such as 0.5 and 0,5.

Fixes #4234

src/tools/pw-cat.c

@@ -1778,6 +1778,7 @@ int main(int argc, char *argv[])
 			break;
 
 		case OPT_VOLUME:
+			if (!spa_atof(optarg, &data.volume))
 				data.volume = (float)atof(optarg);
 			break;
 		default:

src/tools/pw-loopback.c

@@ -163,6 +163,7 @@ int main(int argc, char *argv[])
 			data.latency = atoi(optarg) * DEFAULT_RATE / SPA_MSEC_PER_SEC;
 			break;
 		case 'd':
+			if (!spa_atof(optarg, &data.delay))
 				data.delay = (float)atof(optarg);
 			break;
 		case 'C':