Revamp method coverage to support define_method

Traditionally, method coverage measurement was implemented by inserting
`trace2` instruction to the head of method iseq.  So, it just measured
methods defined by `def` keyword.

This commit drastically changes the measuring mechanism of method
coverage; at `RUBY_EVENT_CALL`, it keeps a hash from rb_method_entry_t*
to runs (i.e., it counts the runs per method entry), and at
`Coverage.result`, it creates the result hash by enumerating all
`rb_method_entry_t*` objects (by `ObjectSpace.each_object`).

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61023 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/run-lcov.rb

@@ -87,15 +87,15 @@ def gen_rb_lcov(file)
 
       # function coverage
       total = covered = 0
-      cov[:methods].each do |(name, _, lineno), count|
-        f.puts "FN:#{ lineno },#{ name }"
+      cov[:methods].each do |(klass, name, lineno), count|
+        f.puts "FN:#{ lineno },#{ klass }##{ name }"
         total += 1
         covered += 1 if count > 0
       end
       f.puts "FNF:#{ total }"
       f.puts "FNF:#{ covered }"
-      cov[:methods].each do |(name, _), count|
-        f.puts "FNDA:#{ count },#{ name }"
+      cov[:methods].each do |(klass, name, _), count|
+        f.puts "FNDA:#{ count },#{ klass }##{ name }"
       end
 
       # line coverage