In order to be able to swich on and off PtrGuard usage, SyncBuffer
implements a typical usage pattern of PtrGuard, that is a data buffer
referenced from inside a C allocated struct, in two ways: 1) using a
PtrGuard to dierctly store a pointer to the Go buffer in C memory, or
2) allocating a C buffer of same size and syncing data back with
C.memcpy(). The implementation can be chosen with the with_ptrguard
build tag.
Signed-off-by: Sven Anderson <sven@redhat.com>
