Fix missing asprintf definition on Haiku

It needs _GNU_SOURCE and is declared in stdio.h as on GNU/Linux,
but I suppose it's not included by the existing includes.

cmake/Conky.cmake

@@ -122,6 +122,15 @@ if(OS_SOLARIS)
   set(conky_libs ${conky_libs} -L/usr/local/lib)
 endif(OS_SOLARIS)
 
+if(OS_HAIKU)
+  # For asprintf
+  add_definitions(-D_GNU_SOURCE) # Standard definitions
+  set(
+    CMAKE_REQUIRED_DEFINITIONS
+    "${CMAKE_REQUIRED_DEFINITIONS} -D_GNU_SOURCE"
+    )
+endif(OS_HAIKU)
+
 # Do version stuff
 set(VERSION_MAJOR "1")
 set(VERSION_MINOR "19")

src/timeinfo.cc

@@ -35,6 +35,7 @@
 #include <clocale>
 #include <cstring>
 #include <ctime>
+#include <stdio.h>
 #include "conky.h"
 #include "logging.h"
 #include "text_object.h"