[gcov] Display the hit counter for the line of a function definition

Summary:
Right now there is no hit counter on the line of function.
So the idea is add the line of the function to all the lines covered by the entry block.
Tests in compiler-rt/profile will be fixed in another patch: https://reviews.llvm.org/D49854

Reviewers: marco-c, davidxl

Reviewed By: marco-c

Subscribers: sylvestre.ledru, llvm-commits

Differential Revision: https://reviews.llvm.org/D49853

llvm-svn: 344228