cmd/gc: add missing entries to lexn and yytfix.

Makes gc -x better.

LGTM=r
R=golang-codereviews, bradfitz, r
CC=golang-codereviews
https://golang.org/cl/73090043

src/cmd/gc/lex.c

@@ -2171,14 +2171,18 @@ struct
 } lexn[] =
 {
 	LANDAND,	"ANDAND",
+	LANDNOT,	"ANDNOT",
 	LASOP,		"ASOP",
 	LBREAK,		"BREAK",
 	LCASE,		"CASE",
 	LCHAN,		"CHAN",
 	LCOLAS,		"COLAS",
+	LCOMM,		"<-",
 	LCONST,		"CONST",
 	LCONTINUE,	"CONTINUE",
+	LDDD,		"...",
 	LDEC,		"DEC",
+	LDEFAULT,	"DEFAULT",
 	LDEFER,		"DEFER",
 	LELSE,		"ELSE",
 	LEQ,		"EQ",
@@ -2205,6 +2209,7 @@ struct
 	LRANGE,		"RANGE",
 	LRETURN,	"RETURN",
 	LRSH,		"RSH",
+	LSELECT,	"SELECT",
 	LSTRUCT,	"STRUCT",
 	LSWITCH,	"SWITCH",
 	LTYPE,		"TYPE",
@@ -2235,6 +2240,7 @@ struct
 	"LASOP",	"op=",
 	"LBREAK",	"break",
 	"LCASE",	"case",
+	"LCHAN",	"chan",
 	"LCOLAS",	":=",
 	"LCONST",	"const",
 	"LCONTINUE",	"continue",