Don't use underscore prefix, for -Wreserved-identifier compatibility

[seanm]

I've never used ragel, but another project I work on does, and it seems code ragel generates has warnings with clang's -Wreserved-identifier (because it uses an underscore prefix in variable/function names), ex:

_simple_lexer_actions, _simple_lexer_key_offsets, _simple_lexer_trans_keys, etc.

At least, I'm pretty sure this is code ragel generates. Please shoot me down if not. :)

The code is here.