a) remove opIsUse(), opIsDefOnly(), opIsDefAndUse()
    b) add isUse(), isDef()
    c) rename opHiBits32() to isHiBits32(),
              opLoBits32() to isLoBits32(),
              opHiBits64() to isHiBits64(),
              opLoBits64() to isLoBits64().

This results to much more readable code, for example compare
"op.opIsDef() || op.opIsDefAndUse()" to "op.isDef()" a pattern used
very often in the code.

llvm-svn: 10461