Add wrappers for *xattr calls

Conflicts:
	debian/control
Fix *xattr prototype mismatches
Wrap all *xattr additions inside HAVE_ tests
Make t.xattr silently succeed on platforms without setcap/getcap
Disable xattr functions on __APPLE__ for now

The eight supported *xattr functions on __APPLE__ all have
different prototypes from the same-named Linux versions and will
require more changes to be supported properly.
Patch from David Bartley to wrap acl_get_fd and acl_get_file.  closes: #521178.
Merge remote-tracking branch 'mackyle/pull-request' into upstream
Merge branch 'upstream'
Bump to Standards-Version 3.9.4.
Build-depend on libcap-dev and libcap2-bin on Linux.
changelog for 1.19-1
Patch from Colin Watson to use appropriate strip command when cross-building.  closes: #693975.
changelog for 1.19-2