Failures in store.exp caused by regcache

[Andrew Cagney]

> (Or rather, by the value code's interaction with the regcache)
> 
> Andrew, this is more your area; I'd like your advice before I dig any
> further.  Here's what's going wrong.  Consider the command sequence:
> "up; print u; set u = s_1; print u".
>   - u has class LOC_REGISTER
>   - The register's home is memory
>   - read_var_value therefore returns an lval_memory
>   - the value of the register is in the register unwind cache at this point
>   - we modify the memory backing the store
>   - we have no way to tell that we've just modified the value of a saved
>     register on the stack
>   - the second print returns the cached value
> 
> So, what do we do?

Flush the frame cache.

Andrew