autoconf: check for mkstemps
autoconf: check for mkstemps

mkstemps is missing on uClibc, and until recently was also missing with
musl-libc. Add an explicit check for this function.

Signed-off-by: Florian Fainelli <59190c1867e3222b932a0de3c668eb2d980d69a2@gmail.com>

mtmiller/stoken,cernekee/stoken,mtmiller/stoken,mtmiller/stoken,cernekee/stoken,cernekee/stoken,mtmiller/stoken,cernekee/stoken