feat: new Math triggers (Clamp, Sign, Atan2, Rad, Deg, Lerp) and char triggers (Angle, Scale, OffSet, Alpha)

[Wftk]

• fix: Rgba sprites mask inverse when palfx invertall = 1.
  Before fix:
  
  After fix:
  
  Char link

New Math triggers:

• Clamp(x,min,max) (float)
  Return a value clamped to an inclusive range of two specified numbers

• Sign(value) (int)
  Returns the sign of a real number. If value < 0 return -1. If value 0 return 0. if value > 0 return 1.

• Atan2(x,y) (float)
  Returns the arc tangent of the two numbers x and y.

• Rad(value) (float)
  Converts degress to radians.

• Deg(value) (float)
  Converts radians to degress.

• Lerp(a,b,amount) (float)
  Linear interpolation between two values.

New Char triggers:

• Angle (float)
  Gets the value of the player's angle.
  Example: "trigger1 = angle < 90"
• Scale (float) (Arguments x, y)
  Gets the value of the player's scale.
  Example: "trigger1 = scale x< 2 || scale y > 2"
• OffSet (float) (Arguments x, y)
  Gets the value of the player's offset.
  Example: "trigger1 = offset x > 20 || offset y > 15"
• Alpha (int) (Arguments source, dest)
  Gets the value of the player's alpha.
  Example: "trigger1 = alpha source > 128 || alpha dest < 64"

[K4thos]

some changes before the PR can be merged:

1. These should be changed to OC_ex variants:
   OC_angle
   OC_scale_x
   OC_scale_y
   OC_offset_x
   OC_offset_y
   OC_alpha_s
   OC_alpha_d

2. script.go references every single existing trigger, even if adding them is not needed because of exisitng lua variants (in such case they should be added as comments). Following triggers are missing in script.go:
   atan2
   clamp
   deg
   lerp
   rad
   sign

3. In script.go the function is named offsetDest instead of alphaDest.

4. Please keep the alphabetical order when adding new functions to that file, let's keep the existing conventions

[K4thos]

This branch has conflicts that must be resolved