The CLI and server main loop now have no conditional JNI code. All JNI
code has been moved into separate source files, which #include the new
"jni_common.h" instead of <jni.h>. The "cli.h" header no longer
includes <jni.h>, so the rest of the Serval source code is now
unaffected by JNI definitions.
The 'cf_limbo' global variable is now thread-local, so that each thread
has its own independent copy of the loaded configuration. The JNI
server entry point now calls cf_init() once. The new 'cf_initialised'
flag prevents clobbering the config state by redundant calls to
cf_init().
The CLI "stop" command now sends SIGHUP to the specific thread in which
the server is running. This is achieved by writing the PID and TID
(Linux Thread ID) into the pidfile, separated by a space, on systems
that support the Linux gettid() and tgkill() system calls. The server's
signal handler has been overhauled, and its logging improved.
