[llvm-cov] Rearrange entries in report index.

[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310518 91177308-0d34-0410-b5e6-96231b3b80d8