MB-5868: Obsolete Mac #includes break in OS X 10.8

Stop using the ancient/obsolete 'flat' include style;
i.e. instead of #include <Gestalt.h> include
<CoreServices/CoreServices.h>

Change-Id: I8ab5f067e12a4d017d5a003fdd6b31c396a34985

configure.ac

@@ -43,7 +43,6 @@ case $host_os in
      SRC_OS="darwin"
      AC_DEFINE(DARWIN,[],[running on MacOS X])
      AC_DEFINE(SIGAR_TEST_OS_DARWIN, [1], [for the tests])
-     SIGAR_INCLUDES="-I /Developer/Headers/FlatCarbon/"
      SIGAR_LIBS="-framework IOKit -framework CoreServices"
      ;;
      *netbsd*)

src/os/darwin/darwin_sigar.c

@@ -50,9 +50,8 @@
 #endif
 #include <mach-o/dyld.h>
 #define __OPENTRANSPORTPROVIDERS__
-#include <Gestalt.h>
-#include <CFString.h>
 #include <CoreFoundation/CoreFoundation.h>
+#include <CoreServices/CoreServices.h>
 #include <IOKit/IOBSD.h>
 #include <IOKit/IOKitLib.h>
 #include <IOKit/IOTypes.h>