As discussed in GCC bug 97088
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97088), parameters in
prototypes of library functions should use reserved names, or no name
at all.
This patch removes the 'x' parameter name from
extern int __isinff (float);
extern int __isinfd (double);
extern int __isnanf (float);
extern int __isnand (double);
extern int __fpclassifyf (float);
extern int __fpclassifyd (double);
extern int __signbitf (float);
extern int __signbitd (double);
to avoid possible clashes with user code in case someone uses
before including Newlib's math.h (or uses some other conflicting
definition)