Fix gcc "unused-but-set-variable" warning in vtkParse.tab.c.

Change-Id: Iac998a7ad59408a7df95b29c9c5ac8673b1d0d8e
Merge topic 'yyhrsloc-set-but-not-used' into master

e6dd94e7 Fix gcc "unused-but-set-variable" warning in vtkParse.tab.c.