[Ironruby-core] Code Review: 19compat

[Tomas Matousek]

  tfpt review "/shelveset:19compat;REDMOND\tomat"
  Comment  : 
  Adds LibraryPath19 option. This option allows to set paths to 1.9 libs and is used in -1.9 mode.
  Implements Kernel#trusted?, Kernel#trust, Kernel#untrust. The flag is always settable and not checked anywhere as we don't support Ruby's security model.
  Fixes Array#fill overload ambiguity.
  Fixes Array#== and Hash#== to handle recursive structures properly.

Tomas