Merge branches 'workarounds' and 'bestsource' into feature

meson.build

@@ -1,7 +1,7 @@
 project('Aegisub', ['c', 'cpp'],
         license: 'BSD-3-Clause',
         meson_version: '>=1.0.0',
-        default_options: ['cpp_std=c++14', 'buildtype=debugoptimized'],
+        default_options: ['cpp_std=c++17', 'buildtype=debugoptimized'],
         version: '3.2.2')
 
 cmake = import('cmake')
@@ -145,6 +145,7 @@ else
     endif
 
     opt_var = cmake.subproject_options()
+    opt_var.set_override_option('cpp_std', 'c++14')
     opt_var.add_cmake_defines({
         'wxBUILD_INSTALL': false,
         'wxBUILD_PRECOMP': 'OFF',       # otherwise breaks project generation w/ meson

src/bestsource_common.h

@@ -21,8 +21,6 @@
 
 #ifdef WITH_BESTSOURCE
 
-namespace std { class string_view; }
-
 #include <bsshared.h>
 
 #include <libaegisub/fs_fwd.h>

src/video_provider_bestsource.cpp

@@ -22,8 +22,6 @@
 #ifdef WITH_BESTSOURCE
 #include "include/aegisub/video_provider.h"
 
-namespace std { class string_view; }
-
 #include "bestsource_common.h"
 
 #include "videosource.h"