Xcos: fix for the to_workspace variable length

Xcos: fix for the to_workspace variable length

Linux 32 machines segfaulted whenever a to_workspace variable name exceeded seven characters.

Now, the user can pass variable names up to nineteen characters long.

Nineteen is a maximum because in tows_c.c I add six caracters to the variable name,
and 19+6 is the maximal variable length of Scilab.

Updated the test.

Change-Id: I6a85b37b994e9452f2d732521d5ef4e520b276f9