Fix enum conversion warnings for LLVM/XCode 11 (#44)

* Fix enum conversion warnings for LLVM/XCode 11

* Add int conversion warning back in to optional CFLAGS

* type conversion and integer overflow fix when decoding maps as arrays

* add test for map that is too large to handle as an array

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/src/qcbor_encode.c b/src/qcbor_encode.c
index be72cd5..b17698d 100644
--- a/src/qcbor_encode.c
+++ b/src/qcbor_encode.c
@@ -72,22 +72,20 @@
    pNesting->pCurrentNesting->uMajorType = CBOR_MAJOR_TYPE_ARRAY;
 }
 
-inline static QCBORError Nesting_Increase(QCBORTrackNesting *pNesting,
+inline static uint8_t Nesting_Increase(QCBORTrackNesting *pNesting,
                                           uint8_t uMajorType,
                                           uint32_t uPos)
 {
-   QCBORError nReturn = QCBOR_SUCCESS;
-
    if(pNesting->pCurrentNesting == &pNesting->pArrays[QCBOR_MAX_ARRAY_NESTING]) {
       // Trying to open one too many
-      nReturn = QCBOR_ERR_ARRAY_NESTING_TOO_DEEP;
+      return QCBOR_ERR_ARRAY_NESTING_TOO_DEEP;
    } else {
       pNesting->pCurrentNesting++;
       pNesting->pCurrentNesting->uCount     = 0;
       pNesting->pCurrentNesting->uStart     = uPos;
       pNesting->pCurrentNesting->uMajorType = uMajorType;
+      return QCBOR_SUCCESS;
    }
-   return nReturn;
 }
 
 inline static void Nesting_Decrease(QCBORTrackNesting *pNesting)
@@ -95,13 +93,13 @@
    pNesting->pCurrentNesting--;
 }
 
-inline static QCBORError Nesting_Increment(QCBORTrackNesting *pNesting)
+inline static uint8_t Nesting_Increment(QCBORTrackNesting *pNesting)
 {
    if(1 >= QCBOR_MAX_ITEMS_IN_ARRAY - pNesting->pCurrentNesting->uCount) {
       return QCBOR_ERR_ARRAY_TOO_LONG;
    }
 
-   pNesting->pCurrentNesting->uCount += 1;
+   pNesting->pCurrentNesting->uCount++;
 
    return QCBOR_SUCCESS;
 }