Target FP: Perform Ada fixed-point scaling in target format
One of the few still remaining uses of DOUBLEST in GDB is the Ada front-end
code that handles scaling of Ada fixed-point types. The target format for
those types is some integer format; to convert those values to standard
floating-point representation, that integer needs to be multiplied by a
rational scale factor, given as a pair of numerator and denominator.
To avoid having to deal with long integer arithmetic, the current Ada
front-end code currently performs those scaling operations in host
DOUBLEST arithmetic. To eliminate this use of DOUBLEST, this patch
changes the front-end to instead perform those operations in the
*target* floating-point format (chosing to use the target "long double").
The implementation is mostly straight-forward, using value_cast and
value_binop to perform the target operations.
Scanning in the scale numerator and denominator is now done into
a host "long long" instead of a DOUBLEST, which should be large
enough to hold all possible values. (Otherwise, this can be replaced
by target-format target_float_from_string operations as well.)
Printing fixed-point types and values should be completely unchanges,
using target_float_to_string with the same format strings as current code.