common: switch to newer versions of OSes

Switch from Fedora 31 to 32 and from Ubuntu 19.10 to 20.04.

common: remove unused Coverity job from the Travis build

common: fix description of librpma

examples: add support for USB Ethernet network interfaces

We do not use Coverity now and do not plan to do it
in the near future.

rpma: abs(errno) because ibv_* likes to return -errno

rpma: ibv_post_send and ibv_post_recv return errno

Add support for running examples on SoftRoCE
on a USB Ethernet network interfaces,
which may not have 'state UP',
but only 'UP' and 'state UNKNOWN', for example:

enp0s29u1u3: <BROADCAST,MULTICAST,UP,LOWER_UP> \
 mtu 1500 qdisc fq_codel state UNKNOWN mode DEFAULT \
 group default qlen 1000

is a correct network interface that can be used
for running examples on SoftRoCE.

librpma is a C library to simplify accessing
persistent memory (PMem) and not persistent memory devices.

doc: add pkg-config to Build-Deps

It's not optional for us, yet not a part of usual dev setups.

common: make CMake more verbose

common: roadmap update after release 0.9.0

common: remove broken block for in-source builds

common: generate documentation in the 'manpages' directory

examples: fix setting unset variable STATE_OK

common: remove setting the nonexisting BUILD_BENCHMARKS variable

don't hide info while looking for packages, it helps debugging.

examples: fix error: variable 'is_pmem' set but not used

Fix the compilation error:

examples/09-flush-to-persistent-GPSPM/client.c:99:6: \
 error: variable 'is_pmem' set but not used \
 [-Werror=unused-but-set-variable]

This patch is the second part of the change in #536.

common: enhance custom make targets

The 'STATE_OK' variable was used in the line #23,
but it has never been set in this script,
so the script has been working correctly so far
only because there was always exactly one good (active and up)
network interface.

common: 0.9.0

common: 0.9.0 changelog update

doc: improve formatting

doc: librpma.7: elaborate

Merge pull request #524 from ldorau/rpma-write-the-ON-DEMAND-PAGING-SUPPORT-section-of-librpma.7-manual

rpma: write the 'ON-DEMAND PAGING SUPPORT' section of librpma.7 manual