Fix C declaration of dir functions and types

[andresag01]

Description

This patch fixes the declaration of the DIR type and related functions
so that they can be called from C code. This is necessary when enabling
functionality that uses the filesystem in mbed TLS.

Status

READY

[geky]

This looks like a good solution 👍

[0xc0170]

/morph test

[mbed-bot]

Result: FAILURE

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

/morph test

Output

mbed Build Number: 1702

Example Build failed!

[0xc0170]

@bridadan This is the failure you shown in another PR (seems like master is affected)

[0xc0170]

/morph test

[mbed-bot]

Result: FAILURE

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

/morph test

Output

mbed Build Number: 1713

Test Prep failed!

[geky]

It looks like CI ran out of memory? or it just took longer than 20 minutes? @bridadan

07:34:15  > git -c core.askpass=true fetch --no-tags --progress git@github.com:ARMmbed/mbed-os.git +refs/heads/master:refs/remotes/origin/master +refs/pull/3949/head:refs/remotes/origin/pr/3949 # timeout=20
07:54:15 ERROR: Timeout after 20 minutes
07:54:15 ERROR: Error cloning remote repo 'origin'
07:54:15 Receiving objects:   0% (1/107466)   
Receiving objects:   1% (1075/107466)   
...
Receiving objects:  92% (98869/107466), 91.85 MiB | 5.46 MiB/s  
Receiving objects:  98% (105319/107466), 97.70 MiB | 5.48 MiB/s   
Receiving objects:  98% (105490/107466), 102.93 MiB | 5.38 MiB/s   
07:54:15 	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1719)
07:54:15 	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1463)
...
07:54:15 	at hudson.matrix.MatrixBuild.run(MatrixBuild.java:313)
07:54:15 	at hudson.model.ResourceController.execute(ResourceController.java:98)
07:54:15 	at hudson.model.Executor.run(Executor.java:404)
07:54:15 ERROR: null
07:54:15 Finished: FAILURE

[0xc0170]

/morph test

[mbed-bot]

Result: SUCCESS

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

/morph test

Output

mbed Build Number: 1723

All builds and test passed!