parse-datetime, parse-duration: no 'static inline'

parse-datetime, parse-duration: no 'static inline'

* lib/parse-datetime.y (to_uchar):
* lib/parse-duration.c (str_const_to_ul, str_const_to_l)
(scale_n_add):
Now static, not static inline.
* m4/parse-datetime.m4 (gl_PARSE_DATETIME):
* modules/parse-duration (configure.ac):
Do not require AC_C_INLINE.