make CFG survive post-reload splitting: SH breakage

[Joern Rennecke]

> Does this patch looks like sensible solution?

This can't possibly work, since split_all_insns is called from toplev.c after
dbr_schedule.

> If so, can you please test it, as I don't have any of the affected platforms

The SH port can be tested with a simulator.  In fact, AFAIK this is the most
common way to test it.

Moreover, you would find this failure if you just tried to build the libraries
with -O2 optimization.

SH targets you can configure are sh-hms/sh-coff and sh-elf.