Provide mathematical, string and aggregate functions for SQL queries
using the SQLite loadable extensions mechanism.

Math functions:

  acos, asin, atan, atn2, atan2, acosh, asinh, atanh, difference,
  degrees, radians, cos, sin, tan, cot, cosh, sinh, tanh, coth,
  exp, log, log10, power, sign, sqrt, square, ceil, floor, pi

String functions:

  replicate, charindex, leftstr, rightstr, ltrim, rtrim, trim,
  replace, reverse, proper, padl, padr, padc, strfilter

Aggregate functions:

  stdev, variance, mode, median, lower_quartile, upper_quartile
