#7 oasys ARMv7 patch

[David Zoller]

This patch updates Atomic-arm.h to use the new atomic functions available in gcc5.3 on an ARMv7 platform (Raspberry Pi). The assembly language instruction that current implementation relies on was deprecated in ARMv6 so I conditionally compile to ue the new functions if the ARM version is >= 6. Hopefully the new functions are available also in v6 but if not this can be tweaked.

The patch also updates gcc.ac to recognize the gcc5.x versions of the compiler as supported. You will need to run build-configure.sh after applying this patch to rebuild the configure script to pick up the gcc.ac changes.