Have made the following changes to the buffer class:

 - Have tried to deprecate that buffer_fread_string() and
   buffer_fwrite_string() methods; these methods embed an integer string
   length in the buffer which gets funny.

 - The buffer_strstr() and buffer_strchr() methods are more robust
   towards binary \0 in the buffer.

 - The buffer_fwrite_char_ptr() function will append a trailing \0.

 - Have added a buffer_strcat() function.