libdfp: Optimize the host to/from ieee functions

This patch changes the way the host to/from ieee copies data by using
word and doubleword loads and store and by also using compiler builtins
for byte swap.
libdfp: Add more coverage for logd tests

This patch adds more coverage for logd test with tests for logd32 and
logd128. It also fixes the file indentation.
libdfp: Fix LE issues with decimal to decNumber

This patch fixes the decimal[32|64|128]FromNumber and decimal[32|64|128]ToNumber
functions for little-endian.