fix exch stack underflow check

- Allow userdata to be linked/included

- bugfixes

- bugfixes
- exch instruction

bugfix

- New preprocessor instructions
- Added the slash character to replace minus for P-Strings

- Added new lua function calling syntax
- Cleaned up pattern generation functions
- Replaced Sliders with more accurate Signals
- Sliders is no longer a dependency of this library

- bugfixes

Replaced sh with << and >>

- Added sh instruction which shifts a pivot location on the top of the stack by some amount.
- $rof can now be negative which indicates direction of travel. $rof is negative if the distance traveled is exactly equal to $hsides.
- $hsides can now be used in a #restrict statement.
- Comments should work again.