Android: Fix compilation on Necessitas Qt SDK v 1.0.0

It is the first experimental patch to start integration of support of Android for QtSerialPort. Therefore for build of library it is necessary to exclude examples and tests.

In this patch should be corrected the tcdrain() function. The main problem is that Android supports this function, beginning from version 4.2 and above:

• https://android.googlesource.com/platform/bionic/+/android-4.2_r1/libc/include/termios.h

But we can't define the Android's API version by means of Q_OS_ANDROID macro yet. Therefore we are stimulated to implement the tcdrain() function manually, having simply copied its implementation from the source codes of
Bionic libc.