CrystaX NDK

Not 100% sure it's not a PJSIP bug, however it compiles fine with vanilla NDK (for now I just renamed the structure "user" defined by PJSIP).

../src/pjmedia/transport_loop.c:31:8: error: redefinition of 'struct user'
struct user
^
In file included from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/sys/user.h:35:0,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/crystax/google/sys/ucontext.h:33,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/sys/ucontext.h:36,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/signal.h:42,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/sys/wait.h:35,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/crystax/sys/stdlib.h:40,
from /home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/stdlib.h:47,
from ../../pjlib/include/pj/compat/string.h:43,
from ../../pjlib/include/pj/string.h:29,
from ../include/pjmedia/frame.h:28,
from ../include/pjmedia/port.h:30,
from ../include/pjmedia/codec.h:29,
from ../include/pjmedia/stream.h:29,
from ../include/pjmedia/transport_loop.h:29,
from ../src/pjmedia/transport_loop.c:20:
/home/adrien/crystax-ndk-10.1.0/platforms/android-15/arch-arm/usr/include/crystax/google/sys/user.h:213:8: note: originally defined here
struct user {
^