make autogenerated functions to be 'static inline' instead of 'inline'

This fixes link issue and compile warning, for more details about this
issue look at
https://bitbucket.org/mjsousa/matiec/issues/53/c-compiler-warning-if-iec-function-is-used

iec.flex.c
iec.y.output
iec.y.cc
iec.y.hh
Makefile.depend