[X86] Clzero flag addition and inclusion under znver1

1. Adds the command line flag for clzero.
2. Includes the clzero flag under znver1.
3. Defines the macro for clzero.
4. Adds a new file which has the intrinsic definition for clzero instruction.

Patch by Ganesh Gopalasubramanian with some additional tests from me.

Differential revision: https://reviews.llvm.org/D29386

llvm-svn: 294559
diff --git a/clang/test/CodeGen/builtin-clflushopt.c b/clang/test/CodeGen/builtin-clflushopt.c
index e98c2aa..9386116 100644
--- a/clang/test/CodeGen/builtin-clflushopt.c
+++ b/clang/test/CodeGen/builtin-clflushopt.c
@@ -3,7 +3,7 @@
 
 #include <immintrin.h>
 void test_mm_clflushopt(char * __m) {
-  //CHECK-LABLE: @test_mm_clflushopt
+  //CHECK-LABEL: @test_mm_clflushopt
   //CHECK: @llvm.x86.clflushopt
   _mm_clflushopt(__m);
 }