std.c: add correct SOMAXCONN for BSDs

Note the previous "28" here for openbsd was some kind of copy
error long ago.  That's the value of KERN.SOMAXCONN, which is an
entirely different thing.

Author: blblack

lib/std/c.zig

@@ -6683,7 +6683,12 @@ pub const SOMAXCONN = switch (native_os) {
     .windows => ws2_32.SOMAXCONN,
     // https://github.com/SerenityOS/serenity/blob/ac44ec5ebc707f9dd0c3d4759a1e17e91db5d74f/Kernel/API/POSIX/sys/socket.h#L128
     .solaris, .illumos, .serenity => 128,
-    .openbsd => 28,
+    // https://github.com/freebsd/freebsd-src/blob/9ab31f821ad1c6bad474510447387c50bef2c24c/sys/sys/socket.h#L434
+    // https://github.com/DragonFlyBSD/DragonFlyBSD/blob/fd3d1949d526ffa646e57037770acd6f2f3bb617/sys/sys/socket.h#L393
+    // https://github.com/NetBSD/src/blob/a673fb3f8487e974c669216064f7588207229fea/sys/sys/socket.h#L472
+    // https://github.com/openbsd/src/blob/8ba9cd88f10123fef7af805b8e5ccc2463ad8fa4/sys/sys/socket.h#L483
+    // https://github.com/apple/darwin-xnu/blob/2ff845c2e033bd0ff64b5b6aa6063a1f8f65aa32/bsd/sys/socket.h#L815
+    .freebsd, .dragonfly, .netbsd, .openbsd, .driverkit, .macos, .ios, .tvos, .watchos, .visionos => 128,
     else => void,
 };
 pub const IFNAMESIZE = switch (native_os) {