test: Match gccgo error messages.

gcc conventionally does not upper case in error messages.

char_lit1.go:13: error: invalid unicode code point 0xd800
char_lit1.go:14: error: invalid unicode code point 0xd999
char_lit1.go:15: error: invalid unicode code point 0xdc01
char_lit1.go:16: error: invalid unicode code point 0xdddd
char_lit1.go:17: error: invalid unicode code point 0xdfff
char_lit1.go:20: error: invalid unicode code point 0x110000
char_lit1.go:22: error: invalid unicode code point 0x110000
char_lit1.go:23: error: invalid unicode code point 0xffffffff

R=rsc
CC=golang-dev
https://golang.org/cl/2040042

test/char_lit1.go

@@ -10,16 +10,16 @@ const (
 	// check that surrogate pair elements are invalid
 	// (d800-dbff, dc00-dfff).
 	_ = '\ud7ff' // ok
-	_ = '\ud800'  // ERROR "Unicode"
-	_ = "\U0000D999"  // ERROR "Unicode"
-	_ = '\udc01' // ERROR "Unicode"
-	_ = '\U0000dddd'  // ERROR "Unicode"
-	_ = '\udfff' // ERROR "Unicode"
+	_ = '\ud800'  // ERROR "Unicode|unicode"
+	_ = "\U0000D999"  // ERROR "Unicode|unicode"
+	_ = '\udc01' // ERROR "Unicode|unicode"
+	_ = '\U0000dddd'  // ERROR "Unicode|unicode"
+	_ = '\udfff' // ERROR "Unicode|unicode"
 	_ = '\ue000' // ok
 	_ = '\U0010ffff'  // ok
-	_ = '\U00110000'  // ERROR "Unicode"
+	_ = '\U00110000'  // ERROR "Unicode|unicode"
 	_ = "abc\U0010ffffdef"  // ok
-	_ = "abc\U00110000def"  // ERROR "Unicode"
-	_ = '\Uffffffff'  // ERROR "Unicode"
+	_ = "abc\U00110000def"  // ERROR "Unicode|unicode"
+	_ = '\Uffffffff'  // ERROR "Unicode|unicode"
 )