Reformat gcconfig.h (related to FreeBSD/arm)

* include/private/gcconfig.h (ALIGNMENT, OS_TYPE, DYNAMIC_LOADING,
HEURISTIC2, etext, SEARCH_FOR_DATA_START): Reformat (adjust
indentation) for FreeBSD/arm.
Fix old_segv/bus_act variables initialization for FreeBSD

* os_dep.c (old_segv_act): Define static variable for FREEBSD (same as
for NETBSD).
* os_dep.c (GC_set_and_save_fault_handler): Reformat code (related to
FreeBSD).
* os_dep.c (GC_reset_fault_handler): Initialize old_segv_act (and
old_bus_act) for FREEBSD (same as for NETBSD).