A fix for PR21176. 
 
DW_OP_const <const> doesn't describe a constant value, but a value at a constant address. 
The proper way to describe a constant value is DW_OP_constu <const>, DW_OP_stack_value. 
Added DW_OP_stack_value to the stack. 

Marked incorrect-variable-debugloc1.ll to xfail for PowerPC64, while the the failure (PR21881) 
is being investigated. 



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224098 91177308-0d34-0410-b5e6-96231b3b80d8