cmd/compile/internal/gc: fix go.y (rename of Fatal -> Fatalf)

Also go generate to update generated files.

Change-Id: I049708db93455f0030ba5afc6f218fde6220958d
Reviewed-on: https://go-review.googlesource.com/14331Reviewed-by: Damien Neil <dneil@google.com>

src/cmd/compile/internal/gc/go.y

@@ -275,7 +275,7 @@ import_stmt:
 		// no package statement. This allows us to test more
 		// than one invalid import statement in a single file.
 		if nerrors == 0 {
-			Fatal("phase error in import");
+			Fatalf("phase error in import");
 		}
 	}
 

src/cmd/compile/internal/gc/y.go

@@ -1057,6 +1057,7 @@ func (yyrcvr *yyParserImpl) Parse(yylex yyLexer) int {
 	var yylval yySymType
 	var yyVAL yySymType
 	var yyDollar []yySymType
+	_ = yyDollar // silence set and not used
 	yyS := make([]yySymType, yyMaxDepth)
 
 	Nerrs := 0   /* number of errors */