Replace getOS() == llvm::Triple::*BSD with isOS*BSD() [NFCI]

Replace multiple comparisons of getOS() value with FreeBSD, NetBSD,
OpenBSD and DragonFly with matching isOS*BSD() methods.  This should
improve the consistency of coding style without changing the behavior.
Direct getOS() comparisons were left whenever used in switch or switch-
like context.

Differential Revision: https://reviews.llvm.org/D55916

llvm-svn: 349752
diff --git a/clang/lib/Basic/Targets/Sparc.h b/clang/lib/Basic/Targets/Sparc.h
index af2189f..5ae305b 100644
--- a/clang/lib/Basic/Targets/Sparc.h
+++ b/clang/lib/Basic/Targets/Sparc.h
@@ -199,7 +199,7 @@
     LongWidth = LongAlign = PointerWidth = PointerAlign = 64;
 
     // OpenBSD uses long long for int64_t and intmax_t.
-    if (getTriple().getOS() == llvm::Triple::OpenBSD)
+    if (getTriple().isOSOpenBSD())
       IntMaxType = SignedLongLong;
     else
       IntMaxType = SignedLong;