all: update for zig-0.13

This is mainly updates to the build system, but there were a couple of
stdlib changes for the tests. The build system does include handling
more properly now as well, I think. It has fewer hacks, at least.

src/connection.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 const Subscription = @import("./subscription.zig").Subscription;
 const SubscriptionCallbackSignature = @import("./subscription.zig").SubscriptionCallbackSignature;

src/error.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 // pub const AllocError = Error || std.mem.Allocator.Error;
 

src/message.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 const err_ = @import("./error.zig");
 const Error = err_.Error;

src/nats.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+pub const nats_c = @import("./nats_c.zig").nats_c;
 
 const err_ = @import("./error.zig");
 const con_ = @import("./connection.zig");

src/nats_c.zig

@@ -0,0 +1,3 @@
+pub const nats_c = @cImport({
+    @cInclude("nats/nats.h");
+});

src/statistics.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 const err_ = @import("./error.zig");
 const Status = err_.Status;

src/subscription.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 const Connection = @import("./connection.zig").Connection;
 

src/thunk.zig

@@ -14,9 +14,7 @@
 
 const std = @import("std");
 
-pub const nats_c = @cImport({
-    @cInclude("nats/nats.h");
-});
+const nats_c = @import("./nats_c.zig").nats_c;
 
 pub fn checkUserDataType(comptime T: type) void {
     switch (@typeInfo(T)) {