Add option to favor 32-bit FADT addresses.

This change adds an option to favor 32-bit FADT addresses when there
is a conflict between the 32-bit and 64-bit versions of the same
address. The default behavior is to use the 64-bit version in accordance
with the ACPI specification. This can now be overridden via the
AcpiGbl_Use32BitFadtAddresses flag. ACPICA BZ 885. Lv Zheng.

Also, the "Convert FADT" and "Verify FADT" functions have been merged to
simplify the code, make it easier to understand, and make it easier to
maintain. ACPICA BZ 933. Bob Moore.