llvm-cov: Combine two types that were nearly identical (NFC)

llvm-cov had a SourceRange type that was nearly identical to a
CountedRegion except that it shaved off a couple of fields. There
aren't likely to be enough of these for the minor memory savings to be
worth the extra complexity here.

llvm-svn: 217417
diff --git a/llvm/tools/llvm-cov/CodeCoverage.cpp b/llvm/tools/llvm-cov/CodeCoverage.cpp
index 6abeef3..549af92 100644
--- a/llvm/tools/llvm-cov/CodeCoverage.cpp
+++ b/llvm/tools/llvm-cov/CodeCoverage.cpp
@@ -36,8 +36,9 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/PrettyStackTrace.h"
-#include <system_error>
 #include <functional>
+#include <system_error>
+#include <unordered_map>
 
 using namespace llvm;
 using namespace coverage;