Add webview suspend and resume functions.

Add webview suspend and resume functions.

[Issue]    https://bugs.tizen.org/jira/browse/TT-208
[Problem]  ewk_view_suspend and ewk_view_resume are not called in
           required moments.
[Cause]    Not implemented function calls.
[Solution] Implement required functions and it's calls.
[Verify]   Open few tabs, try to switch between them.
           Suspend and resume browser.

Change-Id: I9f292a0c316056e3d2c928332bd47a58e9eba23a
Signed-off-by: Dariusz Frankiewicz <d.frankiewic@samsung.com>