Use DW_AT_high_pc and DW_AT_low_pc for the high and low pc for a

Use DW_AT_high_pc and DW_AT_low_pc for the high and low pc for a
compile unit. Make these relocations on the platforms that need
relocations and add a routine to ensure that we don't put the
addresses in an offset table for split dwarf.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199990 91177308-0d34-0410-b5e6-96231b3b80d8