#139 Invalid system flags when using the official castem.h header for Cast3M 2018

[Helfer Thomas]

The castem.h header relies on the definition of some system flags to work appropriately (in particular to define the cast_int typedef). This file changed in Cast3M 2018.
The system flags defined by TFEL/MFront (-DSUN -DUNIX64 or -DSUN -DUNIX32) are no more appropriate under Linux and must be changed to -DLINUX64 or -DLINUX32.

This is fixed in:

• revision 2135 in rliv-3.1
• revision 2136 in trunk