The libio/bits/stdio2-decl.h only defined the prototypes for
__vasprintf_chk and __vfprintf_chk for __USE_FORTIFY_LEVEL > 1.
Also defined them for the internal header regardless.
Checked with a build with --enable-fortify-source=1 and
--enable-fortify-source=2 for all afftected ABIs.
#ifndef _ISOMAC
libc_hidden_proto (__fgets_unlocked_chk)
libc_hidden_ldbl_proto (vfprintf)
+extern int __vasprintf_chk (char **, int, const char *, __gnuc_va_list) __THROW;
libc_hidden_ldbl_proto (__vasprintf_chk)
+extern int __vfprintf_chk (FILE *, int, const char *, __gnuc_va_list);
libc_hidden_ldbl_proto (__vfprintf_chk)
#endif