Alloc-free conversions between bytes, strings and runes.

At the moment supports the following conversion:

• []byte -> string using BytesToString()/B2S()
• string -> []byte using StringToBytes()/S2B()
• []byte -> []rune using AppendBytesToRunes()/AppendB2R()
• []rune -> []byte using AppendRunesToBytes()/AppendR2B()
• string -> []rune using AppendStringToRunes()/AppendS2R()
• []rune -> string using AppendRunesToString()/AppendR2S()

All functions perform fast conversions using unsafe cast or buffer approach.