add test: show locate failing in record punning

in presence of a shadowing definition

tests/test-dirs/locate/record_pun.t

@@ -0,0 +1,51 @@
+############
+With punning
+############
+
+  $ cat > func.ml <<EOF
+  > module M = struct
+  >   type t = { foo : int }
+  > 
+  >   let foo = 42
+  > end
+  > 
+  > let foo = 43
+  > 
+  > let m = { M.foo }
+  > 
+  > EOF
+
+With punning we jump to the definition of the value and not the record:
+  $ $MERLIN single locate -look-for ml -position 9:14 \
+  > -filename ./func.ml < ./func.ml |
+  > jq '.value.pos'
+  {
+    "line": 4,
+    "col": 6
+  }
+
+###############
+Without punning
+###############
+
+  $ cat > func.ml <<EOF
+  > module M = struct
+  >   type t = { foo : int }
+  > 
+  >   let foo = 42
+  > end
+  > 
+  > let foo = 43
+  > 
+  > let m = { M.foo }
+  > 
+  > EOF
+
+FIXME should jump to the re-definition of `foo` line 7
+  $ $MERLIN single locate -look-for ml -position 9:14  \
+  > -filename ./func.ml < ./func.ml |
+  > jq '.value.pos'
+  {
+    "line": 4,
+    "col": 6
+  }