* Emit label debug info w/o location
* Insert debug label call
* Slight refactor for later fix
* Improve debug labels for block statements
* Improve debug info with for loops
* Generate label lbBlocks w/ debug
* Lightly refactor lb_add_debug_label
* Revise comments, add null check assertion
* Use LLVM-C API for debug labels
* Prefer C DILabel API for POSIX, fallback to CPP
* Use version check for LLVM-C DILabel