Fixes warnings and mismatches in printf format strings:
Adds attribute annotations to ublksrv_{log,printf} to get more validation for their invocations.
Addresses warnings for u64s in qcow code; from my read, __u64 ends up an unsigned long long but u64 (in qcow*.cpp) ends up a uint64_t, which should be paired with PRIx64 and PRIu64 format specifier constants (and on my platform ends up not being an unsigned long long).
Adds %zd/%zu in a few places where size_t values are formatted.
Fixes warnings and mismatches in printf format strings:
ublksrv_{log,printf}to get more validation for their invocations.u64s inqcowcode; from my read,__u64ends up anunsigned long longbutu64(inqcow*.cpp) ends up auint64_t, which should be paired withPRIx64andPRIu64format specifier constants (and on my platform ends up not being anunsigned long long).%zd/%zuin a few places wheresize_tvalues are formatted.