misc/bbedit: support append, other builtins

R=golang-dev, PeterGo, adg
CC=golang-dev
https://golang.org/cl/2791042

misc/bbedit/Go.plist

@@ -6,15 +6,22 @@
 	BBLMColorsSyntax = YES;
 	BBLMIsCaseSensitive = YES;
 	BBLMKeywordList = (
+		append,
 		bool,
 		break,
 		byte,
 		cap,
 		case,         
 		chan,
+		close,
+		closed,
 		cmplx,
+		complex,
+		complex128,
+		complex64,
 		const,
 		continue,
+		copy,
 		default,      
 		defer,
 		else,
@@ -43,8 +50,12 @@
 		new,
 		nil,
 		package,
+		panic,
+		print,
+		println,
 		range,
 		real,
+		recover,
 		return,
 		select,
 		string,