[f32] Add conversion routines.

[Zeda]

Higher priority

• f32toa - Convert an f32 float to a string to be displayed.
  • Currently this is emulated by converting the f32 to a "single" and then using singletostr to convert to a string. This means that the f32 library requires mulSingle and the single constants instead of using the already available f32mul and f32 constants.
• atof32 - convert a string to an f32 float.

Integer conversions

• f32toi8
• i8tof32
• f32toi16
• i16tof32
• f32tou8
• u8tof32
• f32tou16
• u16tof32

Conversions between floats

• f32tosingle
• singletof32
• f32tof24
• f24tof32
• f32tof16
• f16tof32
• f32tox
• xtof32
• f32tof64
• f64tof32
• f32toTIFloat
• TIFloattof32