Added default module launch api functionality

1. As in hipModuleLaunchKernel(..., kernelParams, nullptr); works with this commit
    2. Added headers AMDGPUPTNote.h, AMDGPURuntimeMetadata.h to do code object meta data parsing
    3. Changed CMake to look at llvm link libraries
    4. HIP developer should set env variable LLVM_HOME to remove link errors
    5. HIP depends on installed LLVM (not source, not build)
    6. Added sample to test out the feature
    7. Right now HCC does not support embedding metadata in code object. Use clang opencl
    8. Changed HIPCC to read LLVM_HOME env var
    9. New argument to CMake should be given -DLLVM_HOME=<where llvm 5.0 is installed>

Change-Id: Iba38194aa872d97cc2c90a8e5ff746c48055c868


[ROCm/hip-tests commit: 219343027f]

projects/hip-tests/samples/0_Intro/module_api/test.cl

@@ -0,0 +1,12 @@
+__kernel void memset(char in, __global int* out) {
+int tx = get_global_id(0);
+out[tx] = in;
+}
+
+
+__kernel void vadd(__global float *Ad, __global float *Bd, __global float *Cd, int N){
+int tx = get_global_id(0);
+if(tx < N){
+Cd[tx] = Ad[tx] + Bd[tx];
+}
+}