without failing the overall pipeline.

This reverts commit d970e1e7b4.

It is broken and I don't know how to fix it.

 - Fix more deprecated Robot Framework syntax
 - Remove log following
 - Remove some artefacts in teardown
 - Restore use of demjson

It can be useful to know if stack usage will be too high.

If was removed in:
03eabb4c57

Drone 0.8 and Drone 1.x are not fully compatible.

Different perltidy versions format code differently.

and embedded styles

It is mostly redundant.

It turned out that clang significantly slower than gcc on rspamd code
(at least with -O0). Switch off torch to decrease build time.

Build clang plugin and use it to check rspamd printf-like functions
(rspamd_printf, rspamd_fprintf, rspamd_default_log_function, e.t.c).

Compilation with -O2/-O3 is slow.

luacov-coveralls merge mode (-j flag) was created to join reports
containing coverage for different source files (e.g. C and Lua code).
Coverage for the same file in two report is not merged, instead one
source file is added several times to source_files array in JSON. As
a result if we use luacov-coveralls -j on report for same source files
it ends up spending a lot of time on parsing and dumping big JSON files.

This change reduces functional test time from 7+ minutes to 4+ minutes.

Remove all but the last failing keyword inside `BuiltIn.Wait Until
Keyword Succeeds` to reduce amount of useless information in robot log.

Remove all but the last failing keyword inside `BuiltIn.Wait Until
Keyword Succeeds` to reduse amount of useless inforamtion in robot log.

* pagination is disabled by --batch
* use options order like in gdb docs

With indentation block literal is not folded as expected.

It is not currently used.

Sending functional test log (about 5Mb) in a email attachmend was temporary
solution.
Upload them to https://ci.rspamd.com/testlogs/ instead.
Link to log/report will be printed in build log.