unistr/u8-strcmp: Avoid collision with libc function on Solaris 11.
* lib/unistr.in.h (u8_strcmp) [__sun]: Declare with real name
u8_strcmp_gnu.
* modules/unistr/u8-strcmp (configure.ac): Bump version number.
unistr/base: Avoid link errors when module 'libunistring' is also used.
* lib/unistr.in.h (u8_mbtouc_unsafe, u16_mbtouc_unsafe,
u32_mbtouc_unsafe, u8_mbtouc, u16_mbtouc, u32_mbtouc, u8_mbtoucr,
u16_mbtoucr, u32_mbtoucr, u8_uctomb_aux, u16_uctomb_aux, u32_uctomb):
Declare also when HAVE_LIBUNISTRING is set.
Reported by Pádraig Brady <P@draigbrady.com>.