Make wxLogInfo() work even without wxLog::SetVerbose()

It's confusing that wxLogInfo() and wxLogVerbose() are exactly the same and
the former, and not only the latter, doesn't do anything unless SetVerbose()
had been called, even if the log level is wxLOG_Info or higher.

Fix this by checking for GetVerbose() in wxLogVerbose() only and making
wxLogInfo() check the log level only. This makes it very similar to
wxLogMessage() but this is not such a bad thing.

Also improve wxLogVerbose() documentation.

docs/changes.txt

@@ -59,6 +59,8 @@ All:
 
 - Add support for the micro version (third component) to OS and toolkit version
   functions. See wxGetOsVersion(), wxPlatformInfo, and wxAppTraits.
+- wxLogInfo() now logs messages if the log level is high enough, even without
+  wxLog::SetVerbose() which now only affects wxLogVerbose().
 
 wxMSW: