fixed various warnings and obvious errors reported by clang compiler and the coverity tool.

modules/core/src/dxt.cpp

@@ -1801,11 +1801,11 @@ private:
     UMat twiddles;
     String buildOptions;
     int thread_count;
-    bool status;
     int dft_size;
+    bool status;
 
 public:
-    OCL_FftPlan(int _size): dft_size(_size), status(true)
+    OCL_FftPlan(int _size) : dft_size(_size), status(true)
     {
         int min_radix;
         std::vector<int> radixes, blocks;

modules/core/src/ocl.cpp

@@ -1324,6 +1324,9 @@ OCL_FUNC(cl_int, clReleaseEvent, (cl_event event), (event))
 
 #endif
 
+#ifdef _DEBUG
+#define CV_OclDbgAssert CV_DbgAssert
+#else
 static bool isRaiseError()
 {
     static bool initialized = false;
@@ -1335,10 +1338,6 @@ static bool isRaiseError()
     }
     return value;
 }
-
-#ifdef _DEBUG
-#define CV_OclDbgAssert CV_DbgAssert
-#else
 #define CV_OclDbgAssert(expr) do { if (isRaiseError()) { CV_Assert(expr); } else { (void)(expr); } } while ((void)0, 0)
 #endif