Gluer doesn't extract jump targets within if-delimited blocks

[epeguero]

The gluer can extract if delimited blocks, but it currently doesn't bring in its corresponding jump targets.

Building programs-phil/spad/if-delim-test shows that these labels can occur after the return instruction (e.g., jr ra, ret, etc.), so at least these "auxiliary labels" must be extracted and glued as well. (The gluing function already implements this functionality for scalar code). This might be sufficient in most cases if we assume "if" branch targets are always placed at the end; otherwise, we'll have to bring in all of the vector code labels just in case.

Let me know if you guys want to take a stab at this one, or if you'd prefer if I implemented this.

[pbb59]

I would be surprised if the branch targets are always placed after the return of the function. But others might know more.

[epeguero]

I would be surprised if the branch targets are always placed after the return of the function. But others might know more.

Probably not a good assumption, though it might work for some benchmarks (e.g., programs-phil/spad/if-delim-test). Regardless, labels after ret must be extracted. This is the remaining functionality to implement, since 'junk' blocks can be repurposed as auxiliary blocks for if-blocks.