reg_equiv_memory_loc vs. garbage collection

[Joern Rennecke]

> This is an SH specific problem, as the SH port is the only one that 
> defines the ALLOCATE_INITIAL_VALUE macro.  The definition in 
> config/sh/sh.h has no comment, so I don't know what it is doing.  It 
> also turns out that this is code you wrote.  So you probably should try 
> to fix it yourself.

I've already got a patch, but I can't test it in the mainline at the moment,
because that is broken.