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/spell.h

@@ -0,0 +1,33 @@
+#ifndef NEOVIM_SPELL_H
+#define NEOVIM_SPELL_H
+
+int spell_check(win_T *wp, char_u *ptr, hlf_T *attrp, int *capcol,
+                int docount);
+int spell_move_to(win_T *wp, int dir, int allwords, int curline,
+                  hlf_T *attrp);
+void spell_cat_line(char_u *buf, char_u *line, int maxlen);
+char_u *did_set_spelllang(win_T *wp);
+void spell_delete_wordlist(void);
+void spell_free_all(void);
+void spell_reload(void);
+int spell_check_msm(void);
+void ex_mkspell(exarg_T *eap);
+void ex_spell(exarg_T *eap);
+void spell_add_word(char_u *word, int len, int bad, int idx, int undo);
+void init_spell_chartab(void);
+int spell_check_sps(void);
+void spell_suggest(int count);
+void ex_spellrepall(exarg_T *eap);
+void spell_suggest_list(garray_T *gap, char_u *word, int maxcount,
+                        int need_cap,
+                        int interactive);
+char_u *eval_soundfold(char_u *word);
+void ex_spellinfo(exarg_T *eap);
+void ex_spelldump(exarg_T *eap);
+void spell_dump_compl(char_u *pat, int ic, int *dir, int dumpflags_arg);
+char_u *spell_to_word_end(char_u *start, win_T *win);
+int spell_word_start(int startcol);
+void spell_expand_check_cap(colnr_T col);
+int expand_spelling(linenr_T lnum, char_u *pat, char_u ***matchp);
+
+#endif // NEOVIM_SPELL_H