parse 'of' branches for macros properly

tests/macros/tlexerex.nim

@@ -0,0 +1,16 @@
+
+import macros
+
+macro match*(s: cstring|string; pos: int; sections: untyped): untyped =
+  for sec in sections.children:
+    expectKind sec, nnkOfBranch
+    expectLen sec, 2
+  result = newStmtList()
+
+when isMainModule:
+  var input = "the input"
+  var pos = 0
+  match input, pos:
+  of r"[a-zA-Z_]\w+": echo "an identifier"
+  of r"\d+": echo "an integer"
+  of r".": echo "something else"