Shift phase angles

`Q = unwrap(`

unwraps the radian phase angles
in a vector `P`

)`P`

. Whenever the jump between consecutive angles is greater
than or equal to *π* radians, `unwrap`

shifts the angles
by adding multiples of ±2*π* until the jump is less than
*π*. If `P`

is a matrix, `unwrap`

operates columnwise. If `P`

is a multidimensional array,
`unwrap`

operates on the first dimension whose size is larger than
1.