Display the uptime in a more readable way

This adds CString::ToTimeStr() which converts a number of seconds into
a human readable time string.


git-svn-id: https://znc.svn.sourceforge.net/svnroot/znc/trunk@1107 726aef4b-f618-498e-8847-2d620e286838

String.h

@@ -129,6 +129,7 @@ public:
 
 	static CString ToPercent(double d);
 	static CString ToByteStr(unsigned long long d);
+	static CString ToTimeStr(unsigned long s);
 
 	bool ToBool() const;
 	short ToShort() const;