Compile MF-NWT on the mac

[juancastilla]

I successfully compiled mfnwt on the mac using pymake. I only encountered one issue halting the compilation process:

./src_temp/gwf2swr7_NWT.f:14361.22:

    dt = SECNDS(T1)                                               
                          1

Error: 'x' argument of 'secnds' intrinsic at (1) must be of kind 4

I fixed this by changing the following code in gwf2swr7_NWT.f:

DOUBLEPRECISION, INTENT(INOUT) :: T1
DOUBLEPRECISION, INTENT(INOUT) :: T2
DOUBLEPRECISION, INTENT(INOUT) :: Ts

to

REAL(4), INTENT(INOUT) :: T1
REAL(4), INTENT(INOUT) :: T2
REAL(4), INTENT(INOUT) :: Ts

This issue appears to be exclusive of gfortran. Compiling other MODFLOW packages may generate other errors. To debug the .f files and achieve compilation, check warnings and errors appearing on the terminal window—they do not appear in the ipython notebook. This would be a nice addition to pymake.

Thanks Chris!