Always flush stdout when reading stdin line by line.

src/espeak-ng.c

@@ -691,6 +691,8 @@ int main(int argc, char **argv)
 			while (fgets(p_text, max, f_text) != NULL) {
 				p_text[max-1] = 0;
 				espeak_Synth(p_text, max, 0, POS_CHARACTER, 0, synth_flags, NULL, NULL);
+				// Allow subprocesses to use the audio data through pipes.
+				fflush(stdout);
 			}
 			if (f_text != stdin) {
 				fclose(f_text);