plFree2dGrid: Free the memory associated
	with a PLFLT matrix allocated using plAlloc2dGrid
    
| 
	    plFree2dGrid
	  ( | f, | 
| nx, | |
| ny ); | 
    Frees a block of memory allocated using plAlloc2dGrid.
    
f
	  (PLFLT_NC_MATRIX
	    A matrix to be freed after allocation by plAlloc2dGrid and all use
	    of the matrix has been completed.
	  
nx, ny
	  (PLINTDimensions of the matrix to be freed.
This function is used in C examples 8, 9, 11, 14, 16, 20, 21, 22, 28, 30.