re2torea: need an check to detect input filename = output filename

[yslan]

If we accidentally use the same name for the input and output, it will overwrite the rea file and corrupt the file. The tool also run to the end without error message.

A simple check would be nice.

To reproduce:

$ ls 
t.re2  t.rea

$ re2torea
Input old .rea and .re2 (source) file name:
t
 Input new .rea (output) file name:
t
 byte swap: F   6.54321003      -2.93127722E+35
         192           3         192
 number of curved sides           0
           1         224 number of bc

The reatore2 has the same issue but it will at least give a runtime error like this

Fortran runtime error: End of file