Subsets the column by going from high indices to low (the reverse of the supported practice)
rev_col_subset(x, start, end)A matrix of dimensions M x N
A unsigned int that indicates the starting column.
A unsigned int that indicates the ending column.
x A matrix with matrix rows displayed in reverse order
Consider a vector x=[[1,2],[3,4]].
By setting start=1 and end=0, the function would output x=[[2,1],[4,1]].
Start and end must be valid C++ matrix locations. (e.g. matrix cols start at 0 and not 1)