Add vim-modeline to render files as POD

GitHub (also) checks the vim-modeline to decide how the file should
be rendered.

These files are all in the POD format so add the vim-modeline so that
GitHub displays them in a formatted way.

(Note: adding `linguist-language=Pod` in .gitattributes does not work,
 I created a GH support ticket for that a month ago but there have
 been little progress on it.)

Author: Bram

Cross/README.new

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 You're reading ./Cross/README.new, describing Perl cross-compilation process.
 NOTE: this file will replace ./Cross/README, after the cross-compilation scheme
 is stabilized.

INSTALL

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you see.
 It is written in the POD format (see F<pod/perlpod.pod>) which is specially
 designed to be readable as is.

PACKAGING

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you
 see.  It is written in the POD format (see pod/perlpod.pod) which is
 specifically designed to be readable as is.

README.aix

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you see.
 It is written in the POD format (see pod/perlpod.pod) which is specially
 designed to be readable as is.

README.amiga

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you
 see. It is written in the POD format (see perlpod manpage) which is
 specially designed to be readable as is.

README.android

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you
 see. It is written in the POD format (see pod/perlpod.pod) which is
 specially designed to be readable as is.

README.bs2000

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 This document is written in pod format hence there are punctuation
 characters in odd places.  Do not worry, you've apparently got the
 ASCII->EBCDIC translation worked out correctly.  You can read more

README.cn

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 如果你用一般的文字编辑器阅览这份文件, 请忽略文中奇特的注记字符.
 这份文件是以 POD (简明文件格式) 写成; 这种格式是为了能让人直接阅读,
 而特别设计的. 关于此格式的进一步信息, 请参考 perlpod 在线文档.

README.cygwin

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you
 see. It is written in the POD format (see F<pod/perlpod.pod>) which is
 specially designed to be readable as is.

README.freebsd

@@ -1,3 +1,5 @@
+# vim: syntax=pod
+
 If you read this file _as_is_, just ignore the funny characters you
 see.  It is written in the POD format (see pod/perlpod.pod) which is
 specifically designed to be readable as is.