Fix lo_send() argument markers by doing 32-bit comparison.

On 64-bit architectures, changing the markers to 64-bit values broke
ABI compatibility, since previously compiled applications would have
undefined values in the top 32 bits.  This patches fixes it by only
checking the bottom 32 bits of the marker values.
For LO_MARKER_A/B fix, use unsigned long instead of uint64_t.

Otherwise, fails to compile on 32-bit platforms.
Merge branch 'x86_64'