Prepare new rc release: 9.3.4-rc4

[t-b]

• Merge cppTango PRs, Backport: appveyor.yml: Add inline deployment on tag push cppTango#690, Backport: CMakeLists.txt: Add option to disable building the test suite cppTango#689
• Upgrade JTango version to something which includes Migrate to Java 11+ JTango#96
• Merge Update changelog for 9.3.4 cppTango#672 (Edit the release date in the file)
• Tag cppTango
• Merge Check mariadbclient version #69
• Merge this PR
• Tag repo as 9.3.4-rc4

Close #70
Close #63

Release notes:

• [ ]

I was wondering whether we should add a reference to #61 issue somewhere too? (In the release > notes or in the warning message).

Area | Release
-----|----------------------------------------------------------------
Updated C++ library to                   | 9.3.4-rc4
Updated Pogo to                            | 9.6.27

- Fix java version detection to only accept java 8 ([#64][pr-64])
- Default to `/usr` for omni automake checks ([#66][pr-66])
- Fix database connection test ([#65][pr-65])
- Warn on buggy mariadb client versions ([#69][pr-69])

[t-b]

Once we have a newer JTango version availbale, I think the "java must be version 8" check has to be revisited.

[bourtemb]

Once we have a newer JTango version availbale, I think the "java must be version 8" check has to be revisited.

Still a problem with Pogo?
tango-controls/pogo#93

[t-b]

@bourtemb I would be in favour of finishing this PR like we have it know, release 9.3.4-rc4. And then move on to create the next rc. It feels not so productive to wait for every rc until everything is in place. Let's just do more rc releases and get integrated what is ready.

[bourtemb]

@bourtemb I would be in favour of finishing this PR like we have it know, release 9.3.4-rc4. And then move on to create the next rc. It feels not so productive to wait for every rc until everything is in place. Let's just do more rc releases and get integrated what is ready.

@t-b, fine with me!