Remove most clang-cl special cases from cpu_id.cc

They are not needed, and due to them there was a call to _xgetbv()
without a declaration of the function.  This used to work because we
implicitly included intrin.h in all translation units with clang-cl, but
we want to stop doing that.

BUG=chromium:592745
R=fbarchard@google.com

Review URL: https://codereview.chromium.org/1780473003 .

source/cpu_id.cc

@@ -10,12 +10,12 @@
 
 #include "libyuv/cpu_id.h"
 
-#if defined(_MSC_VER) && !defined(__clang__)
+#if defined(_MSC_VER)
 #include <intrin.h>  // For __cpuidex()
 #endif
 #if !defined(__pnacl__) && !defined(__CLR_VER) && \
     !defined(__native_client__) && (defined(_M_IX86) || defined(_M_X64)) && \
-    defined(_MSC_VER) && !defined(__clang__) && (_MSC_FULL_VER >= 160040219)
+    defined(_MSC_VER) && (_MSC_FULL_VER >= 160040219)
 #include <immintrin.h>  // For _xgetbv()
 #endif
 
@@ -48,7 +48,7 @@ extern "C" {
     !defined(__pnacl__) && !defined(__CLR_VER)
 LIBYUV_API
 void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
-#if defined(_MSC_VER) && !defined(__clang__)
+#if defined(_MSC_VER)
 // Visual C version uses intrinsic or inline x86 assembly.
 #if (_MSC_FULL_VER >= 160040219)
   __cpuidex((int*)(cpu_info), info_eax, info_ecx);
@@ -71,7 +71,7 @@ void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
   }
 #endif
 // GCC version uses inline x86 assembly.
-#else  // defined(_MSC_VER) && !defined(__clang__)
+#else  // defined(_MSC_VER)
   uint32 info_ebx, info_edx;
   asm volatile (
 #if defined( __i386__) && defined(__PIC__)
@@ -89,7 +89,7 @@ void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
   cpu_info[1] = info_ebx;
   cpu_info[2] = info_ecx;
   cpu_info[3] = info_edx;
-#endif  // defined(_MSC_VER) && !defined(__clang__)
+#endif  // defined(_MSC_VER)
 }
 #else  // (defined(_M_IX86) || defined(_M_X64) ...
 LIBYUV_API