Fix RTOS function prototypes by adding extern "C"
Fix RTOS function prototypes by adding extern "C"

Wrap the file mbed_rtos_storage.h in extern "C". This allows the
functions inside rtx_lib.h to have correct definitions when included
in a C++ file.

This is required for the RTX5 error trapping.

monkiineko/mbed-os,nRFMesh/mbed-os,mmorenobarm/mbed-os,fahhem/mbed-os,CalSol/mbed,catiedev/mbed-os,monkiineko/mbed-os,YarivCol/mbed-os,pradeep-gr/mbed-os5-onsemi,adamgreen/mbed,CalSol/mbed,fahhem/mbed-os,nRFMesh/mbed-os,monkiineko/mbed-os,ryankurte/mbed-os,pradeep-gr/mbed-os5-onsemi,mikaleppanen/mbed-os,YarivCol/mbed-os,pradeep-gr/mbed-os5-onsemi,andcor02/mbed-os,betzw/mbed-os,karsev/mbed-os,catiedev/mbed-os,Archcady/mbed-os,CalSol/mbed,CalSol/mbed,infinnovation/mbed-os,screamerbg/mbed,fahhem/mbed-os,c1728p9/mbed-os,andcor02/mbed-os,Archcady/mbed-os,andcor02/mbed-os,monkiineko/mbed-os,svogl/mbed-os,screamerbg/mbed,svogl/mbed-os,NXPmicro/mbed,mazimkhan/mbed-os,bcostm/mbed-os,bcostm/mbed-os,mazimkhan/mbed-os,mbedmicro/mbed,bcostm/mbed-os,YarivCol/mbed-os,svogl/mbed-os,betzw/mbed-os,NXPmicro/mbed,andcor02/mbed-os,svogl/mbed-os,andcor02/mbed-os,karsev/mbed-os,monkiineko/mbed-os,svogl/mbed-os,adamgreen/mbed,mbedmicro/mbed,NXPmicro/mbed,pradeep-gr/mbed-os5-onsemi,Archcady/mbed-os,mikaleppanen/mbed-os,betzw/mbed-os,NXPmicro/mbed,pradeep-gr/mbed-os5-onsemi,pradeep-gr/mbed-os5-onsemi,catiedev/mbed-os,kjbracey-arm/mbed,c1728p9/mbed-os,karsev/mbed-os,kjbracey-arm/mbed,HeadsUpDisplayInc/mbed,mmorenobarm/mbed-os,mikaleppanen/mbed-os,fahhem/mbed-os,ryankurte/mbed-os,catiedev/mbed-os,mazimkhan/mbed-os,mbedmicro/mbed,mmorenobarm/mbed-os,ryankurte/mbed-os,screamerbg/mbed,c1728p9/mbed-os,infinnovation/mbed-os,bcostm/mbed-os,HeadsUpDisplayInc/mbed,mmorenobarm/mbed-os,ryankurte/mbed-os,NXPmicro/mbed,fahhem/mbed-os,adamgreen/mbed,infinnovation/mbed-os,YarivCol/mbed-os,HeadsUpDisplayInc/mbed,betzw/mbed-os,karsev/mbed-os,adamgreen/mbed,CalSol/mbed,svogl/mbed-os,YarivCol/mbed-os,CalSol/mbed,mmorenobarm/mbed-os,karsev/mbed-os,catiedev/mbed-os,HeadsUpDisplayInc/mbed,c1728p9/mbed-os,Archcady/mbed-os,c1728p9/mbed-os,Archcady/mbed-os,c1728p9/mbed-os,screamerbg/mbed,HeadsUpDisplayInc/mbed,mbedmicro/mbed,andcor02/mbed-os,Archcady/mbed-os,screamerbg/mbed,mikaleppanen/mbed-os,mikaleppanen/mbed-os,ryankurte/mbed-os,adamgreen/mbed,HeadsUpDisplayInc/mbed,mazimkhan/mbed-os,bcostm/mbed-os,monkiineko/mbed-os,catiedev/mbed-os,ryankurte/mbed-os,nRFMesh/mbed-os,kjbracey-arm/mbed,infinnovation/mbed-os,nRFMesh/mbed-os,mazimkhan/mbed-os,betzw/mbed-os,screamerbg/mbed,mikaleppanen/mbed-os,NXPmicro/mbed,nRFMesh/mbed-os,bcostm/mbed-os,infinnovation/mbed-os,nRFMesh/mbed-os,kjbracey-arm/mbed,karsev/mbed-os,infinnovation/mbed-os,betzw/mbed-os,YarivCol/mbed-os,mazimkhan/mbed-os,mmorenobarm/mbed-os,adamgreen/mbed,fahhem/mbed-os,mbedmicro/mbed