v0.1.23

• Registered functions for a parser can now be accessed via FunctionRegistry::register() (d003841)
• Improved operator strength reduction performance over addition with negative operands (2bf277e, ff81320)
• Improved operator strength reduction performance over subtraction with negative operands (da21685, ff81320)
• Fixed a critical bug where operator strength reduction over subtraction with lvalue=0 resulted in rvalue instead of -rvalue (#11, 4f4aaea, 029e470) (thanks @sylvrs!)