Floating point improvements

- Smaller C: fix a bug in __func__ introduced with
  float-related changes
- make *printf() print floats greater than 1e25
- make *printf() print the plus sign when the format
  includes "+", e.g. printf("%+f\n", 1.0);
- clean up and complete prototypes in <math.h>
- remove non-standard HUGE and LOGHUGE from <math.h>
- add HUGE_VAL to <math.h>
- express some hard-coded limits in terms of constants
  from <float.h>
- uncomment prototypes of several floating point
  conversion functions in <stdlib.h> for Smaller C

include/stdlib.h

@@ -96,12 +96,10 @@ long    random (void);
 char    *setstate (char *);
 void    srandom (unsigned);
 
-#ifndef __SMALLER_C__
 double  atof (const char *);
 double  strtod (const char *, char **);
 char    *ecvt (double, int, int *, int *);
 char    *fcvt (double, int, int *, int *);
 char    *gcvt (double, int, char *);
-#endif
 
 #endif /* _STDLIB_H_ */