BuildSystem: Cleanup userspace directory layout

userspace programs are now in userspace/programs
userspace tests are now in userspace/tests

This makes listing userspace projects much cleaner. Libraries were
already separated to their own directory, so other programs should also.

userspace/programs/http-server/main.cpp

@@ -0,0 +1,73 @@
+#include "HTTPServer.h"
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <stdio.h>
+
+int usage(const char* argv0, int ret)
+{
+	FILE* fout = (ret == 0) ? stdout : stderr;
+	fprintf(fout, "usage: %s [OPTIONS]...\n", argv0);
+	fprintf(fout, "  -h, --help          show this message and exit\n");
+	fprintf(fout, "  -r, --root <PATH>   web root directory\n");
+	fprintf(fout, "  -b, --bind <IPv4>   local address to bind\n");
+	fprintf(fout, "  -p, --port <PORT>   local port to bind\n");
+	return ret;
+}
+
+int main(int argc, char** argv)
+{
+	BAN::StringView root = "/var/www"_sv;
+	BAN::IPv4Address bind = INADDR_ANY;
+	uint16_t port = 80;
+
+	for (int i = 1; i < argc; i++)
+	{
+		if (strcmp(argv[i], "-r") == 0 || strcmp(argv[i], "--root") == 0)
+		{
+			if (i + 1 >= argc)
+				return usage(argv[0], 1);
+			root = argv[i + 1];
+			i++;
+		}
+		else if (strcmp(argv[i], "-b") == 0 || strcmp(argv[i], "--bind") == 0)
+		{
+			if (i + 1 >= argc)
+				return usage(argv[0], 1);
+			bind = inet_addr(argv[i + 1]);
+			if (bind.raw == (in_addr_t)(-1))
+				return usage(argv[0], 1);
+			i++;
+		}
+		else if (strcmp(argv[i], "-p") == 0 || strcmp(argv[i], "--port") == 0)
+		{
+			if (i + 1 >= argc)
+				return usage(argv[0], 1);
+			char* end = NULL;
+			errno = 0;
+			unsigned long value = strtoul(argv[i + 1], &end, 10);
+			if (*end || value > 0xFFFF || errno)
+				return usage(argv[0], 1);
+			port = value;
+			i++;
+		}
+		else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0)
+		{
+			return usage(argv[0], 0);
+		}
+		else
+		{
+			return usage(argv[0], 1);
+		}
+	}
+
+	HTTPServer server;
+	if (auto ret = server.initialize(root, bind, port); ret.is_error())
+	{
+		fprintf(stderr, "Could not initialize server: %s\n", strerror(ret.error().get_error_code()));
+		return 1;
+	}
+
+	BAN::Formatter::println(putchar, "Server started on {}:{} at {}", bind, port, server.web_root());
+	server.start();
+}