framework compatible CocoaLumberjack import

With previous import style, the `LOG_ASYNC_ENABLED, LOG_LEVEL_DEF`
macros were not being defined.

@import style module includes are handled differently in ObjC++, causing
problems with out millisecondTimeStamp implementation. Rather than
address that problem head on, I simple reimplemented our millisecond
timestamp method in objective-c, removing our single ObjC++ file.

// FREEBIE

Signal/Signal-Prefix.pch

@@ -7,8 +7,8 @@
 #ifdef __OBJC__
     #import <UIKit/UIKit.h>
     #import <Foundation/Foundation.h>
-    #import <CocoaLumberjack/CocoaLumberjack.h>
 
+    @import CocoaLumberjack;
     #ifdef DEBUG
     static const NSUInteger ddLogLevel = DDLogLevelAll;
     #else

SignalServiceKit/src/TSPrefix.h

@@ -8,9 +8,10 @@
 #import "OWSAnalytics.h"
 #import "OWSDispatch.h"
 #import "iOSVersions.h"
-#import <CocoaLumberjack/CocoaLumberjack.h>
 #import <Foundation/Foundation.h>
 
+@import CocoaLumberjack;
+
 #ifdef DEBUG
 static const NSUInteger ddLogLevel = DDLogLevelAll;
 #else

SignalServiceKit/src/Util/NSDate+OWS.m

@@ -3,7 +3,6 @@
 //
 
 #import "NSDate+OWS.h"
-#import <chrono>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -11,9 +10,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (uint64_t)ows_millisecondTimeStamp
 {
-    uint64_t milliseconds
-        = (uint64_t)(std::chrono::system_clock::now().time_since_epoch() / std::chrono::milliseconds(1));
-    return milliseconds;
+    NSDate *now = [self new];
+    return (uint64_t)(now.timeIntervalSince1970 * 1000);
 }
 
 + (NSDate *)ows_dateWithMillisecondsSince1970:(uint64_t)milliseconds