Fix parse.y bad handling of file names in some situations.
Fix parse.y bad handling of file names in some situations.

The YYLLOC_DEFAULT() macro needs to get the .text value even
when the rules are empty.

themperek/iverilog,CastMi/iverilog,CastMi/iverilog,themperek/iverilog,themperek/iverilog,CastMi/iverilog