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/sign_defs.h

@@ -0,0 +1,24 @@
+#ifndef NEOVIM_SIGN_DEFS_H
+#define NEOVIM_SIGN_DEFS_H
+
+// signs: line annotations
+
+typedef struct signlist signlist_T;
+
+struct signlist
+{
+    int id;             /* unique identifier for each placed sign */
+    linenr_T lnum;      /* line number which has this sign */
+    int typenr;         /* typenr of sign */
+    signlist_T *next;   /* next signlist entry */
+};
+
+/* type argument for buf_getsigntype() */
+#define SIGN_ANY	0
+#define SIGN_LINEHL	1
+#define SIGN_ICON	2
+#define SIGN_TEXT	3
+
+
+
+#endif // NEOVIM_SIGN_DEFS_H