endian: port to gcc 4.1 + glibc 2.4 Problem reported by Orgad Shaneh in: https://lists.gnu.org/r/bug-gnulib/2025-09/msg00128.html * lib/endian.in.h (bswap_16, bswap_32, bswap_64) [_GL_BYTESWAP_H]: Declare before using.