Sorry, I did not see David answered this.
You'll get these issues on Linux too, so I believe Android inherited
them. I seem to recall experiencing it with some of the networking
headers, and not the signal stuff.
When you encounter it, re-arrange the order of your C++ includes and
your system includes (either C++ headers first or system headers
first).
Looking at a Linux C++ project that includes them, I have the C
headers first, then the system headers, and finally the C++ headers.
Sorry I don't recall more details. Its been a couple of years since I
experienced it.
Jeff