Use llvm::Triple's methods to parse FreeBSD version numbers.

Who could've thought that FreeBSD would ever reach version 10!
Patch from Dimitry Andric.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142349 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index d2ddf2d..d360269 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -247,11 +247,12 @@
                             MacroBuilder &Builder) const {
     // FreeBSD defines; list based off of gcc output
 
-    // FIXME: Move version number handling to llvm::Triple.
-    StringRef Release = Triple.getOSName().substr(strlen("freebsd"), 1);
+    unsigned Release = Triple.getOSMajorVersion();
+    if (Release == 0U)
+      Release = 8;
 
-    Builder.defineMacro("__FreeBSD__", Release);
-    Builder.defineMacro("__FreeBSD_cc_version", Release + "00001");
+    Builder.defineMacro("__FreeBSD__", Twine(Release));
+    Builder.defineMacro("__FreeBSD_cc_version", Twine(Release * 100000U + 1U));
     Builder.defineMacro("__KPRINTF_ATTRIBUTE__");
     DefineStd(Builder, "unix", Opts);
     Builder.defineMacro("__ELF__");