Fixed compile warning in SkOSWindow_unix.cpp

Fixed following compile time warning:

../src/views/unix/SkOSWindow_Unix.cpp: In member function ‘void SkOSWindow::loop()’:
../src/views/unix/SkOSWindow_Unix.cpp:184:33: warning: ‘KeySym XKeycodeToKeysym(Display*, KeyCode, int)’ is deprecated (declared at /usr/include/X11/Xlib.h:1695) [-Wdeprecated-declarations]
../src/views/unix/SkOSWindow_Unix.cpp:184:74: warning: ‘KeySym XKeycodeToKeysym(Display*, KeyCode, int)’ is deprecated (declared at /usr/include/X11/Xlib.h:1695) [-Wdeprecated-declarations]
../src/views/unix/SkOSWindow_Unix.cpp:199:47: warning: ‘KeySym XKeycodeToKeysym(Display*, KeyCode, int)’ is deprecated (declared at /usr/include/X11/Xlib.h:1695) [-Wdeprecated-declarations]
../src/views/unix/SkOSWindow_Unix.cpp:199:88: warning: ‘KeySym XKeycodeToKeysym(Display*, KeyCode, int)’ is deprecated (declared at /usr/include/X11/Xlib.h:1695) [-Wdeprecated-declarations]

XKeycodeToKeysym is marked as deprecated (https://bugs.freedesktop.org/show_bug.cgi?id=5349). Another related bug: https://bugs.freedesktop.org/show_bug.cgi?id=25732#c4  which suggests to use XkbKeycodeToKeySym instead of this one. Similar issue was fixed in chromium http://code.google.com/p/chromium/issues/detail?id=117274

[bsalomon, 2012-06-19 13:09:11]

LGTM, committed as r4278