The command which we use to get the contents of perforce files at a

specific revision, p4 print, tries to be smart about UTF-8 BOM

characters. If the output is to stdout, even if stdout isn't a terminal,

it will strip the BOM. Unfortunately, we had a difference between

RBTools, which uses p4 print -o, and Review Board, which uses

p4 print, so that the diffs produced by RBTools might not apply

cleanly to the files fetched by Review Board.
This change makes Review Board use p4 print -o so that the source file

will match the one used to create the diffs.

Ran unit tests.