Add a .gitignore file

At least one developer (me) uses git to work on local branches, and this
file does not hurt.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

.gitignore

+Makefile
+Makefile.in
+compile
+configure
+configure.lineno
+config.status
+config.log
+LibVNCServer.spec.in
+LibVNCServer.spec
+x11vnc.spec.in
+.deps
+.libs
+aclocal.m4
+autom4te.cache
+libvncserver-config
+_configs.sed
+config.h
+LibVNCServer*.tar.gz
+upload_beta.sh
+stamp-*
+x11vnc*.tar.gz
+config.h.in
+rfbconfig.h
+rfbconfig.h.in
+install-sh
+missing
+mkinstalldirs
+depcomp
+description-pak
+libvncserver*.deb
+*.o
+*.lo
+CVS
+client_examples/SDLvncviewer
+client_examples/backchannel
+client_examples/ppmtest
+config.guess
+config.sub
+contrib/zippy
+examples/backchannel
+examples/blooptest
+examples/camera
+examples/colourmaptest
+examples/example
+examples/filetransfer
+examples/fontsel
+examples/pnmshow
+examples/pnmshow24
+examples/regiontest
+examples/rotate
+examples/simple
+examples/simple15
+examples/storepasswd
+examples/vncev
+libtool
+libvncclient/libvncclient.la
+libvncserver/libvncserver.la
+rfb/rfbint.h
+test/blooptest
+test/cargstest
+test/copyrecttest
+test/cursortest
+test/encodingstest
+vncterm/LinuxVNC
+vncterm/VNCommand
+vncterm/example
+x11vnc.spec
+x11vnc/x11vnc
+CMakeCache.txt
+cmake_install.cmake
+/CMakeFiles