Binary floating point cleanup. This was an area that was hushed up
a bit when the s390 port was first committed. Time to get it in shape.

This patch 
- completes s390_round_t to list all rounding modes that can appear
  in a convert-to instruction
- adapts function encode_rounding_mode accordingly
- ensures that all s390_round_t -> IRRoundingMode conversions go through
  encode_rounding_mode


git-svn-id: svn://svn.valgrind.org/vex/trunk@2513 8f6e269a-dfd6-0310-a8e1-e2731360e62c
2 files changed