net/sems: fix build on big-endian architectures

This port needs C++11 compiler:
cc1plus: error: unrecognized command line option "-std=c++11"

Additionally, it needs appropriate definitions for big-endian architectures:
/usr/local/poudriere/ports/default/net/sems/work/sems-7400051/core/plug-in/isac/libisac/typedefs.h:80:2: error: #error Please add support for your architecture in typedefs.h

80 | #error Please add support for your architecture in typedefs.h
   |  ^~~~~

PR: 240707
Approved by: nwhitehorn (maintainer), linimon (mentor)