Added refs to lecture 7.

Author: janfrancu

docs/src/lecture_07/lecture.md

@@ -164,7 +164,7 @@ end
 
 Observe that macro dispatch is based on the types of AST that are handed to the macro, not the types that the AST evaluates to at runtime.
 
-## Notes on quotation
+## [Notes on quotation](@id lec7_quotation)
 In the previous lecture we have seen that we can *quote a block of code*, which tells the compiler to treat the input as a data and parse it. We have talked about three ways of quoting code.
 1.  `:(quoted code)`
 2. Meta.parse(input_string)
@@ -239,7 +239,7 @@ Instead, when a macro is given an expression with $ in it, it assumes you're goi
 	run(`touch $(filename)`)
 	```
 
-## Macro hygiene
+## [Macro hygiene](@id lec7_hygiene)
 Macro hygiene is a term coined in 1986. The problem it addresses is following: if you're automatically generating code, it's possible that you will introduce variable names in your generated code that will clash with existing variable names in the scope in which a macro is called. These clashes might cause your generated code to read from or write to variables that you should not be interacting with. A macro is hygienic when it does not interact with existing variables, which means that when macro is evaluated, it should not have any effect on the surrounding code. 
 
 By default, all macros in Julia are hygienic which means that variables introduced in the macro have automatically generated names, where Julia ensures they will not collide with user's variable. These variables are created by `gensym` function / macro.