The errors testcases use -module to obtain a unique module name

Fixes parallel make where each invocation of swig was writing and
deleting the same file resulting in lots of the newly introduced
warning messages:

  On exit, could not delete file xxx.py: No such file or directory

Examples/test-suite/errors/cpp_extra_brackets.i

@@ -1,4 +1,4 @@
-%module cpp_extra_brackets
+%module xxx
 
 // Extra brackets was segfaulting in SWIG-3.0.0
 struct ABC {