hdf5_ep

[svn-r11424] Purpose:
    Code cleanup/bug fix

Description:
    Hoist function call out of inner loop of type conversion by retrieving
source & destination precisions once, outside the loop.

    There's still some overhead because this information is stored in
variables set at run-time, when it's really constant for the particular
machine.  Further work to set compiler macros would allow this code to be
optimized better by the compiler with dead code removal.  We'll continue
to work on this area...

    Also, made new internal H5T_compiler_conv routine static instead of of
private, until we need to reference it from another source code module.

Platforms tested:
    h5committest
    FreeBSD 4.11 (sleipnir)