Fix undefined line numbers in yr_lex_parse_rules_fd.

[msuvajac]

Initializing lexer starting line number to 1 in yr_lex_parse_rules_fd. If uninitialized, bug would manifest itself when e.g. syntax error occurs and wrong line number (random memory) is passed to the user.

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[msuvajac]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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