feat(c/libuv): Add io, fs, signal, core, poll features

Signed-off-by: hackerchai <i@hackerchai.com>

feat(c/libuv): Add io, fs, signal features

Signed-off-by: hackerchai <i@hackerchai.com>

refactor(c/libuv): rename io into libuv

Signed-off-by: hackerchai <i@hackerchai.com>

fix(c/libuv): fix some compile errors

Signed-off-by: hackerchai <i@hackerchai.com>

c/libuv/signal.go

@@ -0,0 +1,30 @@
+package libuv
+
+import (
+	"github.com/goplus/llgo/c"
+	_ "unsafe"
+)
+
+type Signal struct {
+	Unused [0]byte
+}
+
+// llgo:type C
+type SignalCb func(handle *Signal, sigNum c.Int)
+
+//go:linkname UvSignalInit C.uv_signal_init
+func UvSignalInit(loop *Loop, handle *Signal) c.Int
+
+// llgo:link (*Signal).Start C.uv_signal_start
+func (s *Signal) Start(cb SignalCb, signum c.Int) c.Int {
+	return 0
+}
+
+// llgo:link (*Signal).StartOneshot C.uv_signal_start_oneshot
+func (s *Signal) StartOneshot(handle *Signal, cb SignalCb, signum c.Int) c.Int {
+	return 0
+}
+
+func (s *Signal) Init(loop *Loop) int {
+	return UvSignalInit(loop, s)
+}