Set mbed minor and patch version to 0 for master

[bulislaw]

Currently the MBED_VERSION on master is set to 5.2.1 and 5.0.123 which is confusing. I can see two ways of fixit that:

• After we make a release we make a change on master to reflect the last released mbed version
• We set it to 0 to avoid cofusion and set it to release version for release branch. @adbridge favors this solution.

One possible issue with second approach is if someone will get an idea of disabling/enabling features basing on MBED_VERSION macro in their app, not that it would work now very well, so maybe it's not a problem after all.

[0xc0170]

rtos failes (see Travis log) , as it requires some version - this was added some time ago when we updated rtx to newer version. We can remove that check in rtos (this version of rtos will be replaced soon).

We discussed this some time ago but with no result. From me, I would favor the first one plus adding a a suffix. However that breaks the numbering system (something like 5.0.0devel - would increase only for every minor version (5.1.0devel, 5.2.0devel, etc))

cc @adbridge

[adbridge]

Versioning is meaningless on master and nothing should be dependent on this on that branch. If RTOS on master expects a version then that is a bug in RTOS and we should address that there. I think this PR is the correct approach ....

So there is this :
#error "This version of RTOS requires mbed library version > 121"

We are now well past 121, can we not now drop this message ?

[adbridge]

LGTM

[0xc0170]

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 174

All builds and test passed!