Add a test script for counting lines. This can be used instead of the

Add a test script for counting lines. This can be used instead of the
"| grep foo | wc -l | grep 2" idiom used by many tests, so that, for
example, tests don't mistakenly accept a count of 12 when 2 is
expected. Also, the new form is more consice: "| grep foo | count 2".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40988 91177308-0d34-0410-b5e6-96231b3b80d8