[xulrunner] Guard possible crash point

If gl context is not ready when we hit this, we get the
engine crashing.
Merge pull request #2 from rainemak/embedlite_26

[xulrunner] Guard possible crash point
Land  Bug 895047 - typedef char16_t PRUnichar/jschar and all dependencies (make engines compat with upstream API)
Fixed build without X11 in current branch
Merge branch 'embedlite_26' of github.com:tmeshkova/gecko-dev into embedlite_26
[xulrunner] Merge upstream bugfixes. Merge remote-tracking branch 'geckodev/embedlite_26' into nemo_stable_26
Added missing NumericLimits.h file
[xulrunner] Add missing NumericLimits.h. Merge remote-tracking branch 'geckodev/embedlite_26' into nemo_stable_26