Fix data race on reader disconnect

The field .vHandle is used to check the validity of the reader.

It is accessed in write mode in RFUnloadReader() from a thread A while
it is also accessed in read mode in RFWaitForReaderInit() from thread B.

==================
WARNING: ThreadSanitizer: data race (pid=23997)
  Write of size 8 at 0x7b4c000002d8 by thread T5:
    #0 RFUnloadReader PCSC/src/readerfactory.c:1005:20 (pcscd+0xda017) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #1 RFUnInitializeReader PCSC/src/readerfactory.c:1151:8 (pcscd+0xda017)
    #2 removeReader PCSC/src/readerfactory.c:645:2 (pcscd+0xda017)
    #3 _UnrefReader PCSC/src/readerfactory.c:120:3 (pcscd+0xda017)
    #4 RFRemoveReader PCSC/src/readerfactory.c:624:5 (pcscd+0xdd11b) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #5 RFRemoveReader PCSC/src/readerfactory.c:624:5 (pcscd+0xdd11b) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #6 HPRemoveDevice PCSC/src/hotplug_libudev.c:348:4 (pcscd+0xe35af) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #7 HPEstablishUSBNotifications PCSC/src/hotplug_libudev.c:640:6 (pcscd+0xe35af)

  Previous read of size 8 at 0x7b4c000002d8 by main thread:
    #0 RFWaitForReaderInit PCSC/src/readerfactory.c:1426:29 (pcscd+0xddabe) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #1 main PCSC/src/pcscdaemon.c:773:2 (pcscd+0xd8864) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)

  Location is heap block of size 400 at 0x7b4c000001c0 allocated by main thread:
    #0 malloc <null> (pcscd+0x52691) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #1 RFAllocateReaderSpace PCSC/src/readerfactory.c:135:25 (pcscd+0xda3b9) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #2 main PCSC/src/pcscdaemon.c:643:7 (pcscd+0xd85a5) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)

  Thread T5 (tid=24004, running) created by main thread at:
    #0 pthread_create <null> (pcscd+0x53dfd) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #1 ThreadCreate PCSC/src/utils.c:184:8 (pcscd+0xe39bb) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #2 HPRegisterForHotplugEvents PCSC/src/hotplug_libudev.c:763:6 (pcscd+0xe2768) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)
    #3 main PCSC/src/pcscdaemon.c:766:7 (pcscd+0xd8857) (BuildId: db0b27e1c3b409153327b14d9e501205ed34fb6e)

SUMMARY: ThreadSanitizer: data race PCSC/src/readerfactory.c:1005:20 in RFUnloadReader
==================

src/readerfactory.h

@@ -119,7 +119,7 @@ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  FCT_MAP_V3 psFunctions_v3; /**< API V3.0 */
  } psFunctions; /**< driver functions */
 
- LPVOID vHandle; /**< Dlopen handle */
+ _Atomic LPVOID vHandle; /**< Dlopen handle */
  int version; /**< IFD Handler version number */
  int port; /**< Port ID */
  int slot; /**< Current Reader Slot */