Merge behavior of : and = into single = operator for pairs; add assignment with _._ operator in function references

test/tests/function reference dot operator.lua

@@ -0,0 +1,22 @@
+local _={}
+_[9]={}
+_[8]={}
+_[7]={tags=_[9],text="52"}
+_[6]={tags=_[8],text="12"}
+_[5]={_[7]}
+_[4]={_[6]}
+_[3]={"return"}
+_[2]={"text",_[5]}
+_[1]={"text",_[4]}
+return {_[1],_[2],_[3]}
+--[[
+{ "text", { {
+      tags = {},
+      text = "12"
+    } } }
+{ "text", { {
+      tags = {},
+      text = "52"
+    } } }
+{ "return" }
+]]--