* lib/base64.c (BASE64_INLINE): Define.
(base64_to_int): Rename from b64 and make it extern. All uses changed.
(uchar_in_range): Remove. All uses removed.
(isbase64, base64_decode_ctx_init):
Move to lib/base64.h and make inline.
* lib/base64.h: Ignore -Wtype-limits, so that we needn’t
worry about uchar_in_range.
(BASE64_INLINE): Define, and use _GL_INLINE_HEADER_BEGIN.
(isubase64): New function, useful as it as a different signature.
(isbase64): Define in terms of isubase64.
* modules/base64 (Depends-on): Add extern-inline.