Fix clang 3.5.0 warning in libngatm

[dim]

Summary

Fix the following -Werror warning from clang 3.5.0, while building lib/libngatm:

sys/contrib/ngatm/netnatm/saal/saal_sscop.c:4030:32: error: 'break' is bound to current loop, GCC binds it to the enclosing loop [-Werror,-Wgcc-compat]
                } while(sn < sscop->vr_h && !QFIND(&sscop->rbuf, sn));
                                             ^
sys/contrib/ngatm/netnatm/saal/saal_sscop.c:173:4: note: expanded from macro 'QFIND'
                        break;                                          \
                        ^
1 error generated.

The idea is to remove any ambiguity by replacing the macro with an equivalent static inline function.

Test Plan

Compile it, testing it in practice will be hard, as ngatm is mostly dead.

[emaste]

related: http://reviews.llvm.org/D2518

Seems OK to me.

[dim]

Closed by commit rS274698 (authored by @dim).