igmpproxy: bump version to a731683d1a65956fa05024b0597b105fe6a3a122

igmpproxy: bump version to a731683d1a65956fa05024b0597b105fe6a3a122

Adds uclinux support.

Fixes the following musl use standard unsigned integer
types autobuilder failures.
http://autobuild.buildroot.net/results/c6a/c6a6eec34cffb2c7876595b36fb8a01f475583f9/
http://autobuild.buildroot.net/results/943/9432748bf7b1e24db9fcb0a8cce6942fcdf6be5b/
http://autobuild.buildroot.net/results/083/083c61f43c2f1f0dec69d44583b447a0520933b7/

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>