const runtime.mask4

2 uses

	runtime (current package)
		utf8.go#L31: 	mask4 = 0x07 // 0000 0111
		utf8.go#L91: 			r = rune(s[0]&mask4)<<18 | rune(s[1]&maskx)<<12 | rune(s[2]&maskx)<<6 | rune(s[3]&maskx)