Possible bug when optimizing function using branch_if / branch_if_not

[Fabrice Leal]

I think i hit a possible bug in the_jit_block_clean_cfg(jit_function_t) function.

At http://git.savannah.gnu.org/cgit/libjit.git/tree/jit/jit-block.c#n948 opcode may be 126 (JIT_OP_BR_IFALSE) or 127 (JIT_OP_BR_ITRUE) and this call will crash the function compilation (http://git.savannah.gnu.org/cgit/libjit.git/tree/jit/jit-block.c#n821).

For reference it is crashing with this function:

https://pastebin.com/aHQ5mNLw

but if i exchange .L0 and .L1 it works well:

https://pastebin.com/L42fKbqg