Implement cmdutils.c:read_file(), and use it in ffmpeg.c for reading

the second pass encoding log file.

Originally committed as revision 22769 to svn://svn.ffmpeg.org/ffmpeg/trunk

cmdutils.h

@@ -200,4 +200,15 @@ void show_pix_fmts(void);
  */
 int read_yesno(void);
 
+/**
+ * Reads the file with name filename, and puts its content in a newly
+ * allocated 0-terminated buffer.
+ *
+ * @param bufptr puts here the pointer to the newly allocated buffer
+ * @param size puts here the size of the newly allocated buffer
+ * @return 0 in case of success, a negative value corresponding to an
+ * AVERROR error code in case of failure.
+ */
+int read_file(const char *filename, char **bufptr, size_t *size);
+
 #endif /* FFMPEG_CMDUTILS_H */