faster exp10f code

[Joseph Myers]

Also, you'll need to take special care that architectures with 
architecture-specific versions of exp10f (i386, ia64, m68k) do get the new 
symbol version as expected.  Again, see how expf is handled for an example 
(note the special .symver handling in sysdeps/ia64/fpu/e_expf.S - and the 
wrapper handling done in commit f7a0b063e7fc81d0eff1e8b2b169876bdfb4cc44).

-- 
Joseph S. Myers
joseph@codesourcery.com