net: use explicit int casts for net.error_eintr etc in the unix implementation too for consistency with the windows one

Author: spytheman

vlib/net/net_nix.c.v

@@ -23,9 +23,9 @@ fn init() {
 pub const msg_nosignal = 0x4000
 pub const msg_dontwait = C.MSG_DONTWAIT
 
-pub const error_ewouldblock = C.EWOULDBLOCK
-pub const error_einprogress = C.EINPROGRESS
-pub const error_eagain = C.EAGAIN
-pub const error_eintr = C.EINTR
+pub const error_ewouldblock = int(C.EWOULDBLOCK)
+pub const error_einprogress = int(C.EINPROGRESS)
+pub const error_eagain = int(C.EAGAIN)
+pub const error_eintr = int(C.EINTR)
 
 fn C.unlink(&char) int