patch 8.2.1155: Vim9: cannot handle line break inside lambda

Problem:    Vim9: cannot handle line break inside lambda.
Solution:   Pass the compilation context through. (closes #6407, closes #6409)

src/structs.h

@@ -1765,6 +1765,9 @@ typedef struct {
     char_u	*(*eval_getline)(int, void *, int, int);
     void	*eval_cookie;	    // argument for eval_getline()
 
+    // used when compiling a :def function, NULL otherwise
+    cctx_T	*eval_cctx;
+
     // Used to collect lines while parsing them, so that they can be
     // concatenated later.  Used when "eval_ga.ga_itemsize" is not zero.
     // "eval_ga.ga_data" is a list of pointers to lines.