Update to latest stable release armadillo-5.600.2:

• expanded .each_col() and .each_row() to handle out-of-place operations
• added .each_slice() for repeated matrix operations on each slice of a cube

• faster handling of compound expressions by join_rows() and join_cols()

• expanded object constructors and generators to handle size() based specification of dimensions (changes in 5.500)

• faster handling of submatrix rows (changes in 5.500)
• faster clamp() (changes in 5.500)

• fixes for handling sparse matrices (changes in 5.500)

• added find_unique() for finding indices of unique values (changes in 5.400)

• added diff() for calculating differences between consecutive elements (changes in 5.400)
• added cumprod() for calculating cumulative product (changes in 5.400)
• added null() for finding the orthonormal basis of null space (changes in 5.400)
• expanded interp1() to handle repeated locations (changes in 5.400)
• expanded unique() to handle complex numbers (changes in 5.400)
• faster flipud() (changes in 5.400)
• faster row-wise cumsum() (changes in 5.400)
• fix for k-means clustering in gmm_diag class (changes in 5.400)