Allow compilation of PROC_VDB code on Linux host (GC_NO_SYS_FAULT_H)

Allow compilation of PROC_VDB code on Linux host (GC_NO_SYS_FAULT_H)

This is to check that PROC_VDB code compilation is ok.  The code will
not work on a non-Solaris host, of course, because of lack of "pagedata"
file, so -D NO_INCREMENTAL should be additionally specified to avoid
abort during GC initialization (in gctest).

* os_dep.c [PROC_VDB && GC_NO_SYS_FAULT_H]: Do not include sys/fault.h
and sys/procfs.h.
* os_dep.c [PROC_VDB && GC_NO_SYS_FAULT_H] (PG_MODIFIED,
struct prpageheader, struct prasmap): Define explicitly.
* os_dep.c [PROC_VDB && GC_NO_SYS_FAULT_H && CPPCHECK] (GC_read_dirty):
Call GC_noop1 for dummy fields of prpageheader and prasmap.