check for readline availability
check for readline availability

dev/lckdclient.c includes headers from readline but configure.ac doesn't
make sure these headers are available. This commit makes sure
readline/readline.h is present and assumes readline is properly installed
if this header is present

[#59 state:resolved]

Signed-off-by: Matt Colyer <1fa2ef4755a9226cb9a0a4840bd89b158ac71391@colyer.name>

libimobiledevice/libimobiledevice,Tatsh/libimobiledevice,libimobiledevice/libimobiledevice,kalev/libimobiledevice,patweb/libimobiledevice,patweb/libimobiledevice,libimobiledevice-win32/libimobiledevice,libimobiledevice-win32/libimobiledevice,kalev/libimobiledevice,upbit/libimobiledevice,libimobiledevice-win32/libimobiledevice,kalev/libimobiledevice,patweb/libimobiledevice,Tatsh/libimobiledevice,Tatsh/libimobiledevice,upbit/libimobiledevice,libimobiledevice-win32/libimobiledevice,upbit/libimobiledevice,Tatsh/libimobiledevice