Proposed patch: fix negative times in progress display

What steps will reproduce the problem?
1. Render images for an hour or so (possibly 36 minutes of CPU time)
2. Look at the time remaining display

What is the expected output? What do you see instead?
The "to go", "elapsed" and "iter/s" fields will at some point start showing 
negative numbers.  Instead, they should show positive numbers all the time.

What version of the product are you using? On what operating system?
Recent SVN on Linux (Ubuntu 10.04, i386)

Please provide any additional information below.
I've attached a patch that resolves the problem on my system.  Additionally, 
the patch makes real_clock() return a wall-time instead of a cpu-time 
measurement; the rationale for this is further explained in the patch.

The patch is based on svn trunk r130

Original issue reported on code.google.com by jep...@gmail.com on 9 May 2011 at 2:54

Attachments:

0001-use-a-real_clock-that-doesn-t-easily-overflow.patch

mp-lee / mandelbulber

Proposed patch: fix negative times in progress display #11