MSVC: Improve warning options set

The previous code had a set of warnings to disable on MSVC.  But some
of these weren't actually enabled by default anyway, only in higher
MSVC warning levels (/W, maps to meson warning_level).  I rearranged
this so that it is clearer in what MSVC warning level a warning would
have been enabled.  Furthermore, sort them numerically within the
levels.

Moreover, we can add a few warning types to the default set, to get a
similar set of warnings that we get by default with gcc or clang (the
equivalents of -Wswitch and -Wformat).

Reviewed-by: Bryan Green <dbryan.green@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/bf060644-47ff-441b-97cf-c685d0827757@eisentraut.org

meson.build

@@ -2147,13 +2147,21 @@ endforeach
 
 if cc.get_id() == 'msvc'
   cflags_warn += [
-    '/wd4018', # signed/unsigned mismatch
-    '/wd4244', # conversion from 'type1' to 'type2', possible loss of data
-    '/wd4273', # inconsistent DLL linkage
-    '/wd4101', # unreferenced local variable
-    '/wd4102', # unreferenced label
+    # Warnings to disable:
+    # from /W1:
     '/wd4090', # different 'modifier' qualifiers
+    '/wd4273', # inconsistent DLL linkage
+    # from /W2:
+    '/wd4244', # conversion from 'type1' to 'type2', possible loss of data
+    # from /W3:
+    '/wd4018', # signed/unsigned mismatch
+    '/wd4101', # unreferenced local variable [like -Wunused-variable, but there is no "unused" attribute, so too noisy]
     '/wd4267', # conversion from 'size_t' to 'type', possible loss of data
+
+    # Additional warnings to enable:
+    '/w24062', # enumerator 'identifier' in switch of enum 'enumeration' is not handled [like -Wswitch]
+    '/w24102', # unreferenced label [like -Wunused-label]
+    '/w24777', # 'function' : format string 'string' requires an argument of type 'type1', but variadic argument number has type 'type2' [like -Wformat]
   ]
 
   cppflags += [