Emit correct location lists with basic block sections.

This patch addresses multiple things:

1) It ensures that const_value is emitted when possible with basic block
sections.
2) It emits location lists such that the labels are always within the
section boundary.
3) It fixes a bug when the parameter is first used in a non-entry block
which is in a different section from the entry block.

Differential Revision: https://reviews.llvm.org/D85085