s390: Testcases and vbit-tester changes for the following
DFP insns:
- extract basied exponent
- insert biased exponent
- quantize
- reround to significance
Patch by Maran Pakkirisamy (maranp@linux.vnet.ibm.com).
Part of fixing BZ #307113.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13286 a5019735-40e9-0310-863c-91ae7b9d1cf9