v1.9.1 (2.0 release candidate)

This is a release candidate for v2.0 of libqb.

There are a number of important changes here.

1. The soname has been bumped up to 100 to avoid any problems if we need to do any extra releases of libqb 1
2. doxygen2man has been included (imported from knet) so it can be used in other cluster projects. It's not currently used in libqb but I anticipate it will be.

As always please use the signed tarballs below.

The shortlog is:
Chrissie Caulfield (3):
list: fix list handling for gcc10 (#383)
list: #include <stddef.h> in qblist.h (#384)
trie: Don't assume that chars are unsigned < 126 (#386)

Fabio M. Di Nitto (3):
[build] fix configure.ac in release tarball
[build] chown the right file
Doxygen2man (#388)

Ferenc Wágner (2):
Errors are represented as negative values
Allow group access to the IPC directory

Jan Friesse (1):
qblist: Retype ptr in qb_list_entry to char* (#385)

Jan Pokorný (2):
build: bump version for inter-release "plain repo" generated tarballs
build: allow for possible v1 branch continuity by generous SONAME offset

Jonas Witschel (1):
Set correct ownership if qb_ipcs_connection_auth_set() has been used