[libmonodroid] correct excess log level that should be info rather than warning.

[atsushieno]

This should fix #1909

[jonpryor]

This is a wonderfully straightforward solution, but I have one problem with it: It’ll complicate certain Debug scenarios.

Consider: https://github.com/xamarin/xamarin-android/blob/master/Documentation/workflow/DevelopmentTips.md#update-directory

When a Xamarin.Android app launches on an Android device, and the app was built in the Debug configuration, it will create an "update" directory during process startup, printing the created directory to adb logcat:

W/monodroid( 2796): Creating public update directory: `/data/data/Mono.Android_Tests/files/.__override__`

After this change, the above message will only be generated if the developer also does:

adb shell setprop debug.mono.log default

Which is (1) not documented (but could be corrected) and (2) not at all obvious.

I realize it would be far uglier, but I wonder if this would be better, for at least some of the messages:

#ifdef RELEASE
    log_info (LOG_DEFAULT, "Creating public update directory: `%s`", override_dir);
#else   /* ndef RELEASE */
    log_warn (LOG_DEFAULT, "Creating public update directory: `%s`", override_dir);
#endif  /* ndef RELEASE */

-or-, using more macro-fu:

#if defined(RELEASE)
#define log_debug_warn log_info
#else   /* ndef RELEASE */
#define log_debug_warn log_warn
#endif  /* ndef RELEASE */

/* ... */
    log_debug_warn (LOG_DEFAULT, "Creating public update directory: `%s`", override_dir);

[atsushieno]

The actual question is: should this be really printed as WARNING at all?

It is our design choice. I believe this specific usage should be notified only when people have problem and try to diagnose the cause of it. IMO it should raise error when monodroid failed to create the directory, with any additional information that lets people correctly understand why.