[base] Reintroduce `FT_SqrtFixed`.
The general square root calculations are not necessary in FreeType. For vector normalization or length, FreeType uses special functions. It is, however, required in the legacy CFF specifications.
- src/base/ftcalc.c (FT_SqrtFixed): New function that uses both Babylonian and bit-wise algorithms, whichever is faster for the given situation.
- include/freetype/internal/ftcalc.h (FT_Sqrt_Fixed): Declare it.