bug in graphic functions

[GoogleCodeExporter]

1. File "TVout.cpp": in TVout::begin change resolution to:
          return begin(mode,232,174);
2. In sketch: open instance with a resolution of (or above):
          TV.begin(PAL,220,165);
3. Eg.: Use TVout::draw_rect function.

Expected output: a rectangle
Actual output  : system halt (or hang)

Board: Arduino Mega2560 
Lib version: TVout Beta1
OS: Ubuntu 10.04
Arduino GUI version: 1.0.4

It seems that going over 160x120 resolution creates problems on some functions. 
Draw_column and Draw_row works well, fonts works well, but it's not good for 
others geometrical rendering (boxes and lines for sure).
Tested with a residual free memory of more than 670B (does not hang for mem 
lack).

Original issue reported on code.google.com by [email protected] on 17 Jun 2014 at 8:44