[XRootD mover] Fix cgi truncation error.

See merge request !14

E.g. in statement like:

  if ((qpos = info_str.find("tried") != STR_NPOS))

operator '!=' takes precedence over '=' hance in case "tried" is
found 'qpos' is assigned with boolean true, which gets cast into
int of value 1.

Obviously Oracle cleans them up if we never suffered, but the
code reads clean now. The same pattern was used in some
CASTOR to CTA code.

With that the release is ready to be tagged following successful tests.

Fixed compilation against Ceph nautilus: the <memory> header is missing from rados/buffer.h, so for now we include it before including libradosstriper. Some header reshuffling took place too.

Reverted gcc 7 (too many deprecation warnings/errors) and instead enabled a larger C++ feature set with gcc 4.8

Unfortunately the ABI has changed to the point that
the GC daemon build breaks...

This reverts commit 108b6144.

For some reason (?), serrno gets overwritten between the logging and its
processing, therefore an easy workaround is to cache its value.