No longer used hacked liveness_pass_1

This hack was introduced in issue#287 which later becomes endless maintainance pain.

=====

Our previous check_exit_request use `brcond` in the middle of a TranslationBlock which

breaks the assumptions and thus a hack to liveness_pass_1 is used for _all_ brcond instructions

which causes issues for MIPS and many other scenarios.

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This patch also resolves PC not sync-ed when no memory hooks are installed, finally. Now

Unicorn will always have correct PC no matter what happens.

uc.c

@@ -708,6 +708,7 @@ uc_err uc_reg_write(uc_engine *uc, int regid, const void *value)
     if (setpc) {
         // force to quit execution and flush TB
         uc->quit_request = true;
+        uc->skip_sync_pc_on_exit = true;
         break_translation_loop(uc);
     }