hdf5_msb

[svn-r18660] Description:
	Tweak H5detect to be even more careful about its actions, to allow
gcc 4.5 to use '-O3'.  Also, minor code cleanups in H5Tfloat.c

Tested on:
	FreeBSD/64 6.3 (liberty) w/gcc 4.5 & production mode
	(h5committest not necessary/appropriate)