patch 9.0.1388: Amiga: not all builds use gethostname()

Problem:    Amiga: not all builds use gethostname().
Solution:   Use gethostname() for all builds except AROS. (Ola Söder,
            closes #12107)

Author: sodero

src/os_amiga.c

@@ -691,7 +691,7 @@ mch_get_user_name(char_u *s, int len)
     void
 mch_get_host_name(char_u *s, int len)
 {
-#if defined(__amigaos4__) && defined(__CLIB2__)
+#if !defined(__AROS__)
     gethostname(s, len);
 #else
     vim_strncpy(s, "Amiga", len - 1);

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1388,
 /**/
     1387,
 /**/