[[ Bug 19166 ]] Update Mac builds to use libc++

This patch changes the configuration of the Mac builds so that they
are compiled using libc++, using deployment target 10.9 and SDK
10.9.

Additionally, it patches a use of a null PMPrinter in one of the APIs
which is believed to cause a failure of a full Mac distribution
build.

config/mac.gypi

@@ -24,12 +24,13 @@
 		'SHARED_PRECOMPS_DIR': '$(OBJROOT)/Precompiled/$(CURRENT_ARCH)',
 		'GCC_WARN_ABOUT_DEPRECATED_FUNCTIONS': 'NO',
 		'ALWAYS_SEARCH_USER_PATHS': 'NO',
-		'MACOSX_DEPLOYMENT_TARGET': '10.6',
+		'MACOSX_DEPLOYMENT_TARGET': '10.9',
 		'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES',
 		'COPY_PHASE_STRIP': 'NO',
 		'STRIP_INSTALLED_PRODUCT': 'NO',
 		'CLANG_LINK_OBJC_RUNTIME': 'NO',
-		'CLANG_CXX_LANGUAGE_STANDARD': 'c++0x',
+		'CLANG_CXX_LANGUAGE_STANDARD': 'c++11',
+        'CLANG_CXX_LIBRARY': 'libc++'
 	},
 
 	'target_defaults':

engine/src/osxprinter.cpp

@@ -708,7 +708,9 @@ void MCMacOSXPrinter::SetDerivedProperties(void)
 {
 	PMRect t_pm_page_rect, t_pm_paper_rect;
 	PDEBUG(stderr, "SetProperties: PMGetAdjustedPaperRect\n");
-	if (PMGetAdjustedPaperRect(m_page_format, &t_pm_paper_rect) == noErr && PMGetAdjustedPageRect(m_page_format, &t_pm_page_rect) == noErr)
+	if (m_page_format != nullptr &&
+        PMGetAdjustedPaperRect(m_page_format, &t_pm_paper_rect) == noErr &&
+        PMGetAdjustedPageRect(m_page_format, &t_pm_page_rect) == noErr)
 	{
 		int4 t_left;
 		t_left = (int4)floor(t_pm_page_rect . left - t_pm_paper_rect . left);
@@ -733,7 +735,8 @@ void MCMacOSXPrinter::SetDerivedProperties(void)
 
 	PDEBUG(stderr, "SetProperties: PMPrinterGetDescriptionURL\n");
     CFURLRef t_ppd_url = NULL;
-	if (PMPrinterCopyDescriptionURL(m_printer, kPMPPDDescriptionType, &t_ppd_url) == noErr)
+	if (m_printer != nullptr &&
+        PMPrinterCopyDescriptionURL(m_printer, kPMPPDDescriptionType, &t_ppd_url) == noErr)
 	{
 		char *t_ppd_file;
 		t_ppd_file = osx_cfstring_to_cstring(CFURLCopyFileSystemPath(t_ppd_url, kCFURLPOSIXPathStyle), true);