Add the %extra_context directive to lemon, as an alternative to %extra_argument.

Use this to improve the performance of the parser.

FossilOrigin-Name: be47a6f5262a43f477700579512fe7112a0872faedcbbe5c3383d13a08af6440

src/parse.y

@@ -24,8 +24,9 @@
 %token_type {Token}
 %default_type {Token}
 
-// The generated parser function takes a 4th argument as follows:
-%extra_argument {Parse *pParse}
+// An extra argument to the constructor for the parser, which is available
+// to all actions.
+%extra_context {Parse *pParse}
 
 // This code runs whenever there is a syntax error
 //