Fix C declaration of dir functions and types
Fix C declaration of dir functions and types

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.

adamgreen/mbed,fahhem/mbed-os,mbedmicro/mbed,nvlsianpu/mbed,mmorenobarm/mbed-os,ryankurte/mbed-os,screamerbg/mbed,netzimme/mbed-os,svogl/mbed-os,mmorenobarm/mbed-os,betzw/mbed-os,fahhem/mbed-os,mazimkhan/mbed-os,svogl/mbed-os,nvlsianpu/mbed,RonEld/mbed,nvlsianpu/mbed,andcor02/mbed-os,CalSol/mbed,fahhem/mbed-os,arostm/mbed-os,netzimme/mbed-os,karsev/mbed-os,RonEld/mbed,kjbracey-arm/mbed,c1728p9/mbed-os,catiedev/mbed-os,andcor02/mbed-os,CalSol/mbed,infinnovation/mbed-os,nRFMesh/mbed-os,infinnovation/mbed-os,andcor02/mbed-os,fahhem/mbed-os,pradeep-gr/mbed-os5-onsemi,bulislaw/mbed-os,arostm/mbed-os,Archcady/mbed-os,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os,cvtsi2sd/mbed-os,nRFMesh/mbed-os,fanghuaqi/mbed,karsev/mbed-os,bulislaw/mbed-os,pradeep-gr/mbed-os5-onsemi,pradeep-gr/mbed-os5-onsemi,mikaleppanen/mbed-os,screamerbg/mbed,c1728p9/mbed-os,adamgreen/mbed,c1728p9/mbed-os,bcostm/mbed-os,ryankurte/mbed-os,mbedmicro/mbed,mikaleppanen/mbed-os,adamgreen/mbed,fahhem/mbed-os,bulislaw/mbed-os,mazimkhan/mbed-os,betzw/mbed-os,catiedev/mbed-os,YarivCol/mbed-os,cvtsi2sd/mbed-os,screamerbg/mbed,catiedev/mbed-os,mbedmicro/mbed,HeadsUpDisplayInc/mbed,andcor02/mbed-os,kl-cruz/mbed-os,bulislaw/mbed-os,fanghuaqi/mbed,adamgreen/mbed,fahhem/mbed-os,netzimme/mbed-os,svogl/mbed-os,mbedmicro/mbed,mbedmicro/mbed,nvlsianpu/mbed,monkiineko/mbed-os,infinnovation/mbed-os,bcostm/mbed-os,bcostm/mbed-os,YarivCol/mbed-os,fanghuaqi/mbed,mazimkhan/mbed-os,c1728p9/mbed-os,ryankurte/mbed-os,nRFMesh/mbed-os,adamgreen/mbed,adamgreen/mbed,monkiineko/mbed-os,mikaleppanen/mbed-os,catiedev/mbed-os,kjbracey-arm/mbed,kl-cruz/mbed-os,nRFMesh/mbed-os,mikaleppanen/mbed-os,RonEld/mbed,betzw/mbed-os,svogl/mbed-os,karsev/mbed-os,monkiineko/mbed-os,NXPmicro/mbed,pradeep-gr/mbed-os5-onsemi,c1728p9/mbed-os,catiedev/mbed-os,nvlsianpu/mbed,bulislaw/mbed-os,RonEld/mbed,screamerbg/mbed,netzimme/mbed-os,NXPmicro/mbed,NXPmicro/mbed,mmorenobarm/mbed-os,infinnovation/mbed-os,mmorenobarm/mbed-os,HeadsUpDisplayInc/mbed,betzw/mbed-os,ryankurte/mbed-os,bcostm/mbed-os,monkiineko/mbed-os,andcor02/mbed-os,CalSol/mbed,NXPmicro/mbed,fanghuaqi/mbed,karsev/mbed-os,RonEld/mbed,netzimme/mbed-os,Archcady/mbed-os,netzimme/mbed-os,nRFMesh/mbed-os,arostm/mbed-os,karsev/mbed-os,betzw/mbed-os,ryankurte/mbed-os,mmorenobarm/mbed-os,karsev/mbed-os,cvtsi2sd/mbed-os,NXPmicro/mbed,nvlsianpu/mbed,Archcady/mbed-os,Archcady/mbed-os,HeadsUpDisplayInc/mbed,kjbracey-arm/mbed,kl-cruz/mbed-os,bcostm/mbed-os,screamerbg/mbed,bcostm/mbed-os,YarivCol/mbed-os,cvtsi2sd/mbed-os,kl-cruz/mbed-os,NXPmicro/mbed,screamerbg/mbed,infinnovation/mbed-os,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os,fanghuaqi/mbed,arostm/mbed-os,YarivCol/mbed-os,Archcady/mbed-os,betzw/mbed-os,RonEld/mbed,arostm/mbed-os,monkiineko/mbed-os,nRFMesh/mbed-os,HeadsUpDisplayInc/mbed,c1728p9/mbed-os,cvtsi2sd/mbed-os,mikaleppanen/mbed-os,YarivCol/mbed-os,catiedev/mbed-os,mikaleppanen/mbed-os,CalSol/mbed,svogl/mbed-os,mmorenobarm/mbed-os,mazimkhan/mbed-os,YarivCol/mbed-os,CalSol/mbed,kjbracey-arm/mbed,pradeep-gr/mbed-os5-onsemi,monkiineko/mbed-os,andcor02/mbed-os,cvtsi2sd/mbed-os,pradeep-gr/mbed-os5-onsemi,ryankurte/mbed-os,Archcady/mbed-os,kl-cruz/mbed-os,bulislaw/mbed-os,CalSol/mbed,kl-cruz/mbed-os,svogl/mbed-os,arostm/mbed-os,infinnovation/mbed-os