Bump project to C++11 in build system

mqudsi · mqudsi · commit 18dc0e56aedb · 2021-06-27T21:41:11.000-05:00
This is required for some of the std::atomic usages (from the recent
patches) under macOS.
diff --git a/meson.build b/meson.build
@@ -1,5 +1,5 @@
 project('pevents', ['cpp'],
-		default_options: ['warning_level=3'])
+		default_options: ['warning_level=3', 'cpp_std=c++11'])
 
 args = []
 if get_option('wfmo')
