SPU LLVM: Improve SPU code precompilation

[elad335]

• Detect invalid SPU relative branches (rely on the size of the SPU local storage), this would decrease the amount of false positives in SPU code mining.
• Detect 'argument passing' block before the main function.
• Detect tail calls by inspecting the called code of branches too, not just the previous code to the branch.

[Augusto7743]

Thanks very much.