bugfixes; step one for 'var T' as return type support

tests/reject/tvarres1.nim

@@ -0,0 +1,17 @@
+discard """
+  file: "tvarres1.nim"
+  line: 12
+  errormsg: "address of 'bla' may not escape its stack frame"
+"""
+
+var
+  g = 5
+
+proc p(): var int = 
+  var bla: int
+  result = bla
+  
+p() = 45
+
+echo g
+