File.open supports option "r:bom|utf-8" in 1.8 mode, but not in 1.9 mode.
I came across this trying to use the Hoe library (cf. https://github.com/seattlerb/hoe/blob/master/lib/hoe.rb, function read_utf), which works in 1.8, but not in 1.9.
`File.open 'Manifest.txt', "r:bom|utf-8"` will yield the following error stack:
ArgumentError: unknown encoding name - bom|utf-8
from org/jruby/RubyIO.java:1066:in `set_encoding'
from org/jruby/RubyFile.java:464:in `initialize'
from org/jruby/RubyIO.java:1111:in `open'