Add a note about POSIX system requirements.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@28422 b3059339-0415-0410-9bf9-f77b7e298cf2

DOCS/xml/en/install.xml

@@ -25,6 +25,11 @@ answers.
 <title>Software requirements</title>
 
 <itemizedlist>
+<listitem><para>
+  <emphasis role="bold">POSIX system</emphasis> - You need a POSIX-compatible
+  shell and POSIX-compatible system tools like grep, sed, awk, etc. in your
+  path.
+</para></listitem>
 <listitem><para>
   <emphasis role="bold">GNU make</emphasis> 3.81 or later
 </para></listitem>

README

@@ -16,6 +16,8 @@ Also read the man page to learn how to use MPlayer.
 
 
 Requirements:
+- POSIX system: You need a POSIX-compatible shell and POSIX-compatible system
+  tools like grep, sed, awk, etc. in your path.
 - You need a working development environment that can compile programs.
   On popular Linux distributions, this means having the glibc development
   package(s) installed.