Fixed bug #115 "flex-style named definitions cause ambiguity in re2c grammar".

Fixed bug #115 "flex-style named definitions cause ambiguity in re2c grammar".

This commit removes 10 shift/reduce conflicts in bison grammar for re2c.
These conflicts are caused by allowing flex-style named definitions
    name regular-expression
to contain newlines and to be mixed with rules. It's not just some
conflicts in LALR(1) grammar, it is genuine ambiguity as can be observed
from the following example:
    /*!re2c
        name "a"
        "b" "c" {}
    */
which can be parsed in two ways:
    definition -> name "a"
    rule -> "b" "c" {}
and
    definition -> name "a" "b"
    rule -> "c" {}
, both ways being perfectly valid.

This commit resolves ambiguity by forbidding newlines in flex-style
named definitions (conforming to flex syntax). Newline in these
definitions is treated in a special way: lexer emits token 'FID_END',
which marks the end of flex-style named definition in parser.