bug#39291: M-: history doesn't store erroneous input

[Federico Tedin]

> Federico, please look into fixing this regression.
>
> TIA

I found that the minibuffer input string in `read_minibuf' was being
added to the history list after we tried to parse an object from it (if
`expflag' was true). So if the parsing failed, then the value wasn't
added to the history. I'm attaching a patch with my changes.

My only doubt is that now, the call to `string_to_object' (which calls
`read-from-string', which calls `read1', and then `read0') is located
outside the context (not sure what the right term is) set up with
`specbind'. Could this be a problem? Do any of these functions depend on
the context set up in `read_minibuf'?  (They don't appear to, just want
to be sure).

Thanks.

minibuf.patch
Description: patch