New contributor o/ hello, and small diff.

["Dionna Amalie Glaze via newlib" <newlib@sourceware.org>]

Hi y'all! Thank you so much for your work on newlib. It's a fantastic
platform to work with :)

I am looking at getting access to the gethostname symbol in
sys/unistd.h outside of __CYGWIN__ or __rtems__. The following
platforms by C preprocessor symbol would be a helpful addition:
__USE_BSD, __USE_UNIX98, __USE_XOPEN2K

In diff form,
==== /home/dionnaglaze/newlib-cygwin/newlib/src/newlib/libc/include/sys/unistd.h
====
247c247,253
< #if !(defined  (_WINSOCK_H) || defined (_WINSOCKAPI_) || defined
(__USE_W32_SOCKETS))
---
> char *        _EXFUN(mktemp, (char *));
> #endif
>
> #if defined __USE_BSD || defined __USE_UNIX98 || defined __USE_XOPEN2K || \
>     ((defined(__CYGWIN__) || defined(__rtems__)) && \
>     !(defined  (_WINSOCK_H) || defined (_WINSOCKAPI_) || \
>       defined (__USE_W32_SOCKETS)))
250,251d255
< #endif
< char *        _EXFUN(mktemp, (char *));

What is y'all's preferred way to submit such a change?
Thanks!

-- 
-Dionna Glaze, PhD (she/her)