[libiberty and gdb] floatformat_is_valid

[Andrew Cagney]

> +      if (!floatformat_is_valid (floatformat_from_type (type), valaddr))

I get:

.../values.c:744: warning: passing arg 2 of `floatformat_is_valid' 
discards qualifiers from pointer target type

I'll fix it with the other changes.

Andrew