Revert "Utils: Remove old compiler support code"

This reverts commit 8a32bcc5e7.

Broke build with MSVC 2015, update 3

Change-Id: Icb59b70fb00ea2a2ecc8d26c8177d21d82aaccf2
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/utils/smallstringview.h

@@ -31,6 +31,16 @@
 
 #include <cstring>
 
+#pragma push_macro("constexpr")
+#ifndef __cpp_constexpr
+#define constexpr
+#endif
+
+#pragma push_macro("noexcept")
+#ifndef __cpp_noexcept
+#define noexcept
+#endif
+
 namespace Utils {
 
 class SmallStringView
@@ -125,3 +135,6 @@ bool operator!=(const SmallStringView& first, const SmallStringView& second) noe
 }
 
 } // namespace Utils
+
+#pragma pop_macro("noexcept")
+#pragma pop_macro("constexpr")