Implement read_yesno().

Originally committed as revision 18037 to svn://svn.ffmpeg.org/ffmpeg/trunk

cmdutils.c

@@ -472,3 +472,14 @@ void show_formats(void)
 "decoder corresponds to the h263 and h263p encoders, for file formats it is even\n"
 "worse.\n");
 }
+
+int read_yesno(void)
+{
+    int c = getchar();
+    int yesno = (toupper(c) == 'Y');
+
+    while (c != '\n' && c != EOF)
+        c = getchar();
+
+    return yesno;
+}

cmdutils.h

@@ -152,4 +152,10 @@ void show_license(void);
  */
 void show_formats(void);
 
+/**
+ * Returns a positive value if reads from standard input a line
+ * starting with [yY], otherwise returns 0.
+ */
+int read_yesno(void);
+
 #endif /* FFMPEG_CMDUTILS_H */