fix issues with PowerPC / big-endian

[vtjnash]

This fixes two issues:

1. a call to write assumed little-endian, a cast to char is necessary to ensure the addressof operator points to the correct byte
2. a cast from int to char assumes char is signed, this cast needs to be delayed until after the sign test

[rain-1]

Merged rain-1@90ad99e

[vtjnash]

1. was incidentally fixed
2. is still an open issue

[OlliV]

I think the issue is not that you are running big-endian code but that char is unsigned by default on PowerPC (and ARM).