Update docstrings of CustomCompoundBondForce and CustomTorsionForce to specify...

Update docstrings of CustomCompoundBondForce and CustomTorsionForce to specify units and domain of torsion

openmmapi/include/openmm/CustomCompoundBondForce.h

@@ -57,7 +57,7 @@ namespace OpenMM {
  * <li>distance(p1, p2): the distance between particles p1 and p2 (where "p1" and "p2" may be replaced by the names
  * of whichever particles you want to calculate the distance between).</li>
  * <li>angle(p1, p2, p3): the angle formed by the three specified particles.</li>
- * <li>dihedral(p1, p2, p3, p4): the dihedral angle formed by the four specified particles.</li>
+ * <li>dihedral(p1, p2, p3, p4): the dihedral angle formed by the four specified particles, in radians, on the domain [-pi,+pi).</li>
  * </ul>
  *
  * The expression also may involve tabulated functions, and may depend on arbitrary

openmmapi/include/openmm/CustomTorsionForce.h

@@ -69,8 +69,9 @@ namespace OpenMM {
  * computed.  You can then query its value in a Context by calling getState() on it.
  *
  * Expressions may involve the operators + (add), - (subtract), * (multiply), / (divide), and ^ (power), and the following
- * functions: sqrt, exp, log, sin, cos, sec, csc, tan, cot, asin, acos, atan, sinh, cosh, tanh, erf, erfc, min, max, abs, floor, ceil, step, delta, select.  All trigonometric functions
- * are defined in radians, and log is the natural logarithm.  step(x) = 0 if x is less than 0, 1 otherwise.  delta(x) = 1 if x is 0, 0 otherwise.
+ * functions: sqrt, exp, log, sin, cos, sec, csc, tan, cot, asin, acos, atan, sinh, cosh, tanh, erf, erfc, min, max, abs, floor, ceil, step, delta, select.
+ * All trigonometric functions are defined in radians, with the torsion `theta` on the domain [-pi, +pi), and log is the natural logarithm.
+ * step(x) = 0 if x is less than 0, 1 otherwise.  delta(x) = 1 if x is 0, 0 otherwise.
  * select(x,y,z) = z if x = 0, y otherwise.
  */