Misc. macro cleanup

- ROOT_UID's comment is misleading, as it's always defined to 0.

- SEEK_{SET,END} & O_NOFOLLOW should already be defined on Unix-like
  systems in <stdio.h> and <fcntl.h>, respectively.  In any case,
  neither of those #ifdef blocks should be in the middle of source files.

- The S_IS{LNK,DIR,...} macros should only be undefined on Windows.

src/nvim/misc1.c

@@ -2729,13 +2729,6 @@ void fast_breakcheck(void)
   }
 }
 
-#ifndef SEEK_SET
-# define SEEK_SET 0
-#endif
-#ifndef SEEK_END
-# define SEEK_END 2
-#endif
-
 /*
  * Get the stdout of an external command.
  * If "ret_len" is NULL replace NUL characters with NL.  When "ret_len" is not

src/nvim/option.c

@@ -837,9 +837,10 @@ set_option_default (
     } else {  /* P_BOOL */
       *(int *)varp = (int)(intptr_t)options[opt_idx].def_val[dvi];
 #ifdef UNIX
-      /* 'modeline' defaults to off for root */
-      if (options[opt_idx].indir == PV_ML && getuid() == ROOT_UID)
-        *(int *)varp = FALSE;
+      // 'modeline' defaults to off for root
+      if (options[opt_idx].indir == PV_ML && getuid() == 0) {
+        *(int *)varp = false;
+      }
 #endif
       /* May also set global value for local option. */
       if (both)

src/nvim/os/os_defs.h

@@ -34,28 +34,6 @@
 # define DFLT_MAXMEMTOT (10*1024)
 #endif
 
-#if !defined(S_ISDIR) && defined(S_IFDIR)
-# define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
-#endif
-#if !defined(S_ISREG) && defined(S_IFREG)
-# define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
-#endif
-#if !defined(S_ISLNK) && defined(S_IFLNK)
-# define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
-#endif
-#if !defined(S_ISBLK) && defined(S_IFBLK)
-# define S_ISBLK(m) (((m) & S_IFMT) == S_IFBLK)
-#endif
-#if !defined(S_ISSOCK) && defined(S_IFSOCK)
-# define S_ISSOCK(m) (((m) & S_IFMT) == S_IFSOCK)
-#endif
-#if !defined(S_ISFIFO) && defined(S_IFIFO)
-# define S_ISFIFO(m) (((m) & S_IFMT) == S_IFIFO)
-#endif
-#if !defined(S_ISCHR) && defined(S_IFCHR)
-# define S_ISCHR(m) (((m) & S_IFMT) == S_IFCHR)
-#endif
-
 // Note: Some systems need both string.h and strings.h (Savage).  However,
 // some systems can't handle both, only use string.h in that case.
 #include <string.h>

src/nvim/os/win_defs.h

@@ -50,4 +50,26 @@ typedef SSIZE_T ssize_t;
 # endif
 #endif
 
+#if !defined(S_ISDIR) && defined(S_IFDIR)
+# define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
+#endif
+#if !defined(S_ISREG) && defined(S_IFREG)
+# define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
+#endif
+#if !defined(S_ISLNK) && defined(S_IFLNK)
+# define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
+#endif
+#if !defined(S_ISBLK) && defined(S_IFBLK)
+# define S_ISBLK(m) (((m) & S_IFMT) == S_IFBLK)
+#endif
+#if !defined(S_ISSOCK) && defined(S_IFSOCK)
+# define S_ISSOCK(m) (((m) & S_IFMT) == S_IFSOCK)
+#endif
+#if !defined(S_ISFIFO) && defined(S_IFIFO)
+# define S_ISFIFO(m) (((m) & S_IFMT) == S_IFIFO)
+#endif
+#if !defined(S_ISCHR) && defined(S_IFCHR)
+# define S_ISCHR(m) (((m) & S_IFMT) == S_IFCHR)
+#endif
+
 #endif  // NVIM_OS_WIN_DEFS_H

src/nvim/os_unix.c

@@ -175,13 +175,6 @@ void mch_exit(int r)
   exit(r);
 }
 
-#ifndef SEEK_SET
-# define SEEK_SET 0
-#endif
-#ifndef SEEK_END
-# define SEEK_END 2
-#endif
-
 #define SHELL_SPECIAL (char_u *)"\t \"&'$;<>()\\|"
 
 /// Does wildcard pattern matching using the shell.

src/nvim/shada.c

@@ -3082,8 +3082,8 @@ shada_write_file_nomerge: {}
       // viminfo file that the user can't read.
       FileInfo old_info;
       if (os_fileinfo((char *)fname, &old_info)) {
-        if (getuid() == ROOT_UID) {
-          if (old_info.stat.st_uid != ROOT_UID
+        if (getuid() == 0) {
+          if (old_info.stat.st_uid != 0
               || old_info.stat.st_gid != getgid()) {
             const uv_uid_t old_uid = (uv_uid_t) old_info.stat.st_uid;
             const uv_gid_t old_gid = (uv_gid_t) old_info.stat.st_gid;

src/nvim/vim.h

@@ -27,9 +27,6 @@ Error: configure did not run properly.Check auto/config.log.
 # endif
 #endif
 
-/* user ID of root is usually zero, but not for everybody */
-#define ROOT_UID 0
-
 
 /* Can't use "PACKAGE" here, conflicts with a Perl include file. */
 #ifndef VIMPACKAGE
@@ -232,15 +229,6 @@ enum {
 /* Size in bytes of the hash used in the undo file. */
 #define UNDO_HASH_SIZE 32
 
-#ifdef HAVE_FCNTL_H
-# include <fcntl.h>
-#endif
-
-
-#ifndef O_NOFOLLOW
-# define O_NOFOLLOW 0
-#endif
-
 /*
  * defines to avoid typecasts from (char_u *) to (char *) and back
  * (vim_strchr() and vim_strrchr() are now in alloc.c)