We had been actually computing acos(-1) every time we needed PI (duh).
Now we just use the value defined in math.h.  Also, using sincos()
function defined in math.h in place of calling sin() and cos() separately
in dms::SinCos().  This is about 33% faster.  However, sincos() is not a
standard C/C++ function; it is defined in GNU C.  We may need to add a
contingency for non-Linux compiles...

svn path=/branches/KDE_3_0_BRANCH/kdeedu/kstars/; revision=178985