[llvm-cov] Rearrange entries in report index.

Files which don't contain any functions are likely useless; don't
include them in the main table. Put the links at the bottom of the
page, in case someone wants to figure out coverage for code inside
a macro.

Not sure if this is the best solution, but it seems like an
improvement.

Differential Revision: https://reviews.llvm.org/D36298

llvm-svn: 310518
diff --git a/llvm/tools/llvm-cov/SourceCoverageViewHTML.h b/llvm/tools/llvm-cov/SourceCoverageViewHTML.h
index 94b08a5..8cb7356 100644
--- a/llvm/tools/llvm-cov/SourceCoverageViewHTML.h
+++ b/llvm/tools/llvm-cov/SourceCoverageViewHTML.h
@@ -38,6 +38,8 @@
   void emitFileSummary(raw_ostream &OS, StringRef SF,
                        const FileCoverageSummary &FCS,
                        bool IsTotals = false) const;
+  std::string buildLinkToFile(StringRef SF,
+                              const FileCoverageSummary &FCS) const;
 };
 
 /// \brief A code coverage view which supports html-based rendering.