Removed the optimized asm versions of scalb() and scalbf(). These

Removed the optimized asm versions of scalb() and scalbf().  These
functions are only for compatibility with obsolete standards.  They
shouldn't be used, so they shouldn't be optimized.  Use the generic
versions instead.

This fixes scalbf() as a side effect.  The optimized asm version left
garbage on the FP stack.  I fixed the corresponding bug in the optimized
asm scalb() and scalbn() in 1996.  NetBSD fixed it in scalb(), scalbn()
and scalbnf() in 1999 but missed fixing it in scalbf().  Then in 2005
the bug was reimplemented in FreeBSD by importing NetBSD's scalbf().

The generic versions have slightly different error handling:
- the asm versions blindly round the second parameter to a (floating
  point) integer and proceed, while the generic versions return NaN
  if this rounding changes the value.  POSIX permits both behaviours
  (these functions are XSI extensions and the behaviour for a bogus
  non-integral second parameter is unspecified).   Apart from this
  and the bug in scalbf(), the behaviour of the generic versions seems
  to be identical.  (I only exhusatively tested
  generic_scalbf(1.0F, anyfloat) == asm_scalb(1.0F, anyfloat).  This
  covers many representative corner cases involving NaNs and Infs but
  doesn't test exception flags.  The brokenness of scalbf() showed up
  as weird behaviour after testing just 7 integer cases sequentially.)