qprintable.go
func (e *encoder) nextSpecialChar(p []byte) (i int) {
	for i = 0; i < len(p); i++ {
		// ASCII 32-126 (printable) + '\t' - '=' can appear in the qprintable stream
		if !((p[i] >= 32 && p[i] <= 126 && p[i] != byte('=')) || p[i] == byte('\t')) {
			return i
		}
	}
	return i
}
func (e *encoder) nextSpecialChar(p []byte) (i int) {
	for i = 0; i < len(p); i++ {
		// ASCII 32-126 (printable) + '\t' - '=' can appear in the qprintable stream
		if !((p[i] >= 32 && p[i] <= 126 && p[i] != byte('=')) || p[i] == byte('\t')) {
			return i
		}
	}
	return i
}
// Return first character position where the character has to be escaped