Add a proper type for bit arrays

- Define type bitArrayElement_t as uint32_t.
- Add BITARRAY_DECLARE() macro, which declares a bit array given
the number of desired bits, taking care of aligment and rounding
up its size to a multiple of 32.
- Change bit array functions to accept bitarrayElement_t* rather
than void*.
- Replace bit array declarations with BITARRAY_DECLARE() macro
- Add BITARRAY_FIND_FIRST_SET() macro to call bitArrayFindFirstSet()
without explicitely specifying its size.
- Update comments in bitarray.h to reflect these changes.

src/main/fc/fc_msp.c

@@ -417,7 +417,7 @@ static void packBoxModeFlags(boxBitmask_t * mspBoxModeFlags)
     memset(mspBoxModeFlags, 0, sizeof(boxBitmask_t));
     for (uint32_t i = 0; i < activeBoxIdCount; i++) {
         if (activeBoxes[activeBoxIds[i]]) {
-            bitArraySet(mspBoxModeFlags, i);
+            bitArraySet(mspBoxModeFlags->bits, i);
         }
     }
 }