Add API to override log outut handler

Useful when wrapping KSCrash in a framework that has other ways to
log than stdout/files.

Source/KSCrash/Recording/Tools/KSLogger.c

@@ -257,12 +257,25 @@ bool kslog_clearLogFile()
 #pragma mark - C -
 // ===========================================================================
 
+static KSLogFunction g_logFunction = NULL;
+
+void kslog_setOutputFunction(KSLogFunction function)
+{
+    g_logFunction = function;
+}
+
 static void i_kslog_log(const char* const level,
                         const char* const file,
                         const int line,
                         const char* const function,
                         const char* const fmt, va_list args)
 {
+    if (g_logFunction)
+    {
+        g_logFunction(level, file, line, function, fmt, args);
+        return;
+    }
+
     if(level && file && line >= 0 && function)
     {
         writeFmtToLog("%s: %s (%u): %s: ", level, lastPathEntry(file), line, function);

Source/KSCrash/Recording/Tools/KSLogger.h

@@ -153,6 +153,7 @@ extern "C" {
 
 
 #include <stdbool.h>
+#include <stdarg.h>
 
 
 #ifdef __OBJC__
@@ -259,6 +260,20 @@ bool kslog_setLogFilename(const char* filename, bool overwrite);
 /** Clear the log file. */
 bool kslog_clearLogFile();
 
+typedef void (*KSLogFunction)(const char* level, const char* file,
+                     int line, const char* function,
+                     const char* fmt, va_list args);
+
+/** Set the function responsible for logging.
+ * When set, will deliver all logging to this function
+ * instead of the default handler, so stdout output and file
+ * output will be disabled unless the handler has its own
+ * mechanism for dealing with those.
+ *
+ * @param function The function that should handle logging.
+ */
+void kslog_setOutputFunction(KSLogFunction function);
+
 /** Tests if the logger would print at the specified level.
  *
  * @param LEVEL The level to test for. One of: