safe_macros: turn functions with off_t parameter into static inline

Some functions used to implement safe macros have parameters
of type off_t or structures containing off_t fields.

We don't want these to be compiled into libltp, because
some testcases are compiled with different flags such as:
  -D_FILE_OFFSET_BITS=64 -DOFF_T=__off64_t
which then creates incompatibility and testcases can fail.

For example sendfile06_64 on i386:
    sendfile06_64    1  TFAIL  :  sendfile06.c:90: sendfile(2) failed
          to return expected value, expected: 17592186044442, got: 26

Signed-off-by: Jan Stancek <jstancek@redhat.com>
Acked-by: Cyril Hrubis <chrubis@suse.cz>