Conversing arbitrary length data files to matrix

This function converts a data file into a matrix. The data stored in the file has arbitrary length. The function uses dynamic memory to predict the matrix size.

For example: if the data stored in a file named "data.dat" is:
1 2
3
4 5 6 7 8 9
10
After using A = File2Matrix('data.dat'), Matrix A has contents:
A =

1 2 0 0 0 0
3 0 0 0 0 0
4 5 6 7 8 9
10 0 0 0 0 0