🚀 go-pugleaf

Three minor things about libg++ math.h header file.

In libg++ math.h header there is a test for certain systems for which
inline isinf() and isnan() functions are defined. I think sgi should
be included in the test. SGI math library doesn't have isnan() or
isinf() (or I can't just find them). Seems that in libg++ only dtoa()
uses them and it is commented as obsolete so this may not be very
important.

The SGI system headers define finite() to return int which conflicts
with libg++ math.h double return value. I think this is just a typo in
libg++ math.h. Shouldn't finite return int?

It would be nice if the libg++ math.h would include the system math.h
so one could use functions defined there (like sinf(), cosf() etc)
without hardcoding /usr/include to #include or explicitly declaring
the protos.