Simplify some checks by using __CLANG_PREREQ

Summary: [Folly] Simplify some checks by using `__CLANG_PREREQ`.

Reviewed By: meyering

Differential Revision: D2656842

fb-gh-sync-id: e762fba423fb7cc08907d10dc10f8f46d93a9fe4

folly/Range.h

@@ -201,9 +201,7 @@ public:
   constexpr Range(Iter start, size_t size)
       : b_(start), e_(start + size) { }
 
-# if !defined(__clang__) || __clang_major__ > 3 || \
-  (__clang_major__ == 3 && __clang_minor__ > 6)
-  // Clang 3.6 crashes on this line
+# if !__clang__ || __CLANG_PREREQ(3, 7) // Clang 3.6 crashes on this line
   /* implicit */ Range(std::nullptr_t) = delete;
 # endif
 

folly/test/ExceptionWrapperTest.cpp

@@ -18,6 +18,7 @@
 #include <stdexcept>
 #include <folly/ExceptionWrapper.h>
 #include <folly/Conv.h>
+#include <folly/Portability.h>
 
 using namespace folly;
 
@@ -176,12 +177,12 @@ TEST(ExceptionWrapper, with_exception_test) {
   EXPECT_EQ(ew2.class_name(), "IntException");
   ew2.with_exception<AbstractIntException>([&](AbstractIntException& ie) {
       EXPECT_EQ(ie.getInt(), expected);
-#if defined __clang__ && (__clang_major__ > 3 || __clang_minor__ >= 6)
+#if __CLANG_PREREQ(3, 6)
 # pragma clang diagnostic push
 # pragma clang diagnostic ignored "-Wunevaluated-expression"
 #endif
       EXPECT_EQ(typeid(ie), typeid(IntException));
-#if defined __clang__ && (__clang_major__ > 3 || __clang_minor__ >= 6)
+#if __CLANG_PREREQ(3, 6)
 # pragma clang diagnostic pop
 #endif
     });