Fix various warnings

cmake/compilers/msvc.cmake

@@ -29,6 +29,15 @@ add_compile_options("$<$<COMPILE_LANGUAGE:C>:/W4>")
 # There are way too many of these to realistically deal with them
 add_compile_options("$<$<COMPILE_LANGUAGE:C>:/wd4267>")
 
+# C4206: nonstandard extension used: translation unit is empty
+add_compile_options("$<$<COMPILE_LANGUAGE:C>:/wd4206>")
+
+# C4324: 'struct': structure was padded due to alignment specifier
+add_compile_options("$<$<COMPILE_LANGUAGE:C>:/wd4324>")
+
+# C4200: nonstandard extension used: zero-sized array in struct/union
+add_compile_options("$<$<COMPILE_LANGUAGE:C>:/wd4200>")
+
 # MSVC doesn't understand __inline__, which libjpeg uses
 add_compile_definitions(__inline__=inline)