`RubyVM.keep_script_lines`

`RubyVM.keep_script_lines` enables to keep script lines
for each ISeq and AST. This feature is for debugger/REPL
support.

```ruby
RubyVM.keep_script_lines = true
RubyVM::keep_script_lines = true

eval("def foo = nil\ndef bar = nil")
pp RubyVM::InstructionSequence.of(method(:foo)).script_lines
```

1 files changed, 2 insertions, 1 deletions

diff --git a/parse.y b/parse.y
index 9f44ff6235..2ec9d7770c 100644
--- a/parse.y
+++ b/parse.y
@@ -6306,7 +6306,8 @@ yycompile0(VALUE arg)
 	    cov = Qtrue;
 	}
     }
-    if (p->keep_script_lines) {
+
+    if (p->keep_script_lines || ruby_vm_keep_script_lines) {
         if (!p->debug_lines) {
             p->debug_lines = rb_ary_new();
         }