I noticed many commits replacing the log messages in case of allocation
failure with some macros. That is good, bringing consistency, but I
think that we should offer couple of them. The current one is rather dry
(meaning that it offers very few context details), which matches most of
the existing log messages used in such cases.

But there are also other log messages for such cases which give more
details, like for what the allocation fails, some also giving the
requested size of allocation.

So besides the current two macros (one for shm and one for pkg), we
should add few more. Like:

#define PKG_MEM_ERROR_MSG(m) LM_ERR("could not allocate private memory
from pkg pool - %s\n", m);

So one can do:

PKG_MEM_ERROR_MSG("needed for htable struct");

And one to include also the size:

#define PKG_MEM_ERROR_SZ(s, m) LM_ERR("could not allocate private memory
from pkg pool - size: %u - %s\n", (unsigned int)s, m);

No need to revert what was done, but I think for the future we would
preserve better information for troubleshooting in some cases, instead
of replacing those messages that now have more details with the bare
error log message.