gherkin: (C) Avoid using repeated typedefs (support gcc <v4.6)

Technically C does not support repeated typedefs until C11, however
modern compilers do allow it (gcc also using -std=c90). But since
gcc <v4.6 does not support that, remove the usage of them.

gherkin: (C) Avoid using repeated typedefs (support gcc <v4.6)

Technically C does not support repeated typedefs until C11, however
modern compilers do allow it (gcc also using -std=c90). But since
gcc <v4.6 does not support that, remove the usage of them.