Added type conversion intrinsics

1. Added all type conversion intrinsics
2. NO TESTS have been added. (Will add in next commit)
3. Sanatized code in hip_runtime.h
4. Added passed() to hipTestHalf to make it pass on HIT

Change-Id: I0987963c802fc7ff4d7e07d7b88d86da35da53c9


[ROCm/hip commit: 6f2cfddc67]

projects/hip/tests/src/deviceLib/hipTestHalf.cpp

@@ -128,5 +128,5 @@ __global__ void CheckCmpHalf2(hipLaunchParm lp, __half2* In1, __half2* In2, __ha
 }
 
 int main(){
-
+  passed();
 }