```
rtld: remove pointless "extern"
```
```
libsys: internalize memcpy, memset, and strlcpy
```
```
libsys: remove usage of pthread_once and _once_stub
that existed in auxv.c, use simple bool gate instead. This leaves a
small window if two threads try to call _elf_aux_info(3) simultaneously.
The situation is safe because auxv parsing is really idempotent. The
parsed data is same, and we store atomic types (int/long/ptr) so
double-init does not matter.
```
```
libsys: move errno to libsys
```
```
libsys: disable ssp
```