[RFA] Replace strdup with xstrdup in tic30-dis.c

[Doug Evans]

Alan Modra writes:
 > Same goes for definitions.  This is a pain:
 > 
 > int some_func (a, b, c)
 >      boolean                a;
 >      all_lined_up_sweetly * b;
 >      int                    c;
 > 
 > Writing code this way almost guarantees that over time your code will
 > end up looking like:
 > 
 > int some_func (a, b, c)
 >      bfd_boolean                a;
 >      not_lined_up * b;
 >      int                    c;
 > 
 > Ditto local vars.

Amen!