Added the "dtype" argument to function matrix_exponential_rankN.
This is to force the conversion of dtype, if they are of other type. This can be conversion from complex128 to complex64.
Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.
Authored by: tlinnet 2014-06-20
Parent: [r24201]
Child: [r24203]
