package/wavemon: add upstream patch to fix musl/uclibc build issue

package/wavemon: add upstream patch to fix musl/uclibc build issue

In version 0.9.0 wavemon uses the GLIBC-specific extension `on_exit()`
which is not available in musl and uClibc.

According to the Linux kernel man page [1]: "Portable application should
avoid this function, and use the standard atexit(3) instead."

Add patch from upstream which is fixing this issue by dropping
`on_exit()` and using the standard `atexit()` instead. Note, that the commit
message of the upstream patch was changed to add some useful information.

[1] http://man7.org/linux/man-pages/man3/on_exit.3.html

Backported from: f6e20c9c6e9b50963caaf5483248d329473a6815

Fixes:
http://autobuild.buildroot.net/results/ae54441c65fe9a1bdcf743aa7f6a208e5545ca29
http://autobuild.buildroot.net/results/40fd66e6a351a1acd537ade715ab3e993eddb1c1

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>