Move the printing of llvm-cov information out from collectLineCounts().

collectLineCounts() should only organize the output data. This is done in
anticipation of subsequent changes which will pass in GCNO and GCDA filenames
into the print function where it is printed similar to the gcov output.

Patch by Yuchen Wu!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193134 91177308-0d34-0410-b5e6-96231b3b80d8