Introduce nvim namespace: Move files.

Move files from src/ to src/nvim/.
- src/nvim/ becomes the new root dir for nvim executable sources.
- src/libnvim/ is planned to become root dir of the neovim library.

src/nvim/os/uv_helpers.c

@@ -0,0 +1,70 @@
+#include <uv.h>
+
+#include "os/uv_helpers.h"
+#include "vim.h"
+#include "memory.h"
+
+/// Common structure that will always be assigned to the `data` field of
+/// libuv handles. It has fields for many types of pointers, and allow a single
+/// handle to contain data from many sources
+typedef struct {
+  WStream *wstream;
+  RStream *rstream;
+  Job *job;
+} HandleData;
+
+static HandleData *init(uv_handle_t *handle);
+
+RStream *handle_get_rstream(uv_handle_t *handle)
+{
+  RStream *rv = init(handle)->rstream;
+  assert(rv != NULL);
+  return rv;
+}
+
+void handle_set_rstream(uv_handle_t *handle, RStream *rstream)
+{
+  init(handle)->rstream = rstream;
+}
+
+WStream *handle_get_wstream(uv_handle_t *handle)
+{
+  WStream *rv = init(handle)->wstream;
+  assert(rv != NULL);
+  return rv;
+}
+
+void handle_set_wstream(uv_handle_t *handle, WStream *wstream)
+{
+  HandleData *data = init(handle);
+  data->wstream = wstream;
+}
+
+Job *handle_get_job(uv_handle_t *handle)
+{
+  Job *rv = init(handle)->job;
+  assert(rv != NULL);
+  return rv;
+}
+
+void handle_set_job(uv_handle_t *handle, Job *job)
+{
+  init(handle)->job = job;
+}
+
+static HandleData *init(uv_handle_t *handle)
+{
+  HandleData *rv;
+
+  if (handle->data == NULL) {
+    rv = xmalloc(sizeof(HandleData));
+    rv->rstream = NULL;
+    rv->wstream = NULL;
+    rv->job = NULL;
+    handle->data = rv;
+  } else {
+    rv = handle->data;
+  }
+
+  return rv;
+}