Clarify build requirements

Document the need for the XSI Extension.  Don't list curses as
required, it's actually optional.  Correct advice for Solaris.  Add
advice for AIX.  Drop references to C89; we actually require C99, and
POSIX.1-2001 provides it.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

README

@@ -26,8 +26,9 @@ To build the server and set up a game, follow the steps below.
 
 (2) Building a server
 
-    Prerequisites: IEEE Std 1003.1-2001 (POSIX.1-2001), GNU make, a
-    curses library, Perl, and either nroff or GNU troff (`groff').
+    Prerequisites: IEEE Std 1003.1-2001 (POSIX.1-2001) with the X/Open
+    System Interfaces Extension, GNU make, Perl, and either nroff or
+    GNU troff (`groff').
 
     See file `INSTALL' for detailed compilation and installation
     instructions.  Quick guide for the impatient: run configure; make;
@@ -48,9 +49,14 @@ To build the server and set up a game, follow the steps below.
     GNU make.  Some systems have it installed as `gmake'.
 
     Solaris supports POSIX.1-2001, but you need to set up your
-    environment for that.  Try passing
-        SHELL=/usr/xpg4/bin/sh PATH=/usr/xpg6/bin:/usr/xpg4/bin:$PATH
-    to make.  See standards(5) for details.
+    environment for that.  Try
+
+        SHELL=/usr/xpg4/bin/sh
+        PATH=/usr/xpg6/bin:/usr/xpg4/bin:/usr/ccs/bin:$PATH
+
+    See standards(5) for details.
+
+    Likewise, AIX needs XPG_SUS_ENV=ON.
 
 (3) Creating a game
 

configure.ac

@@ -32,9 +32,9 @@
 # Process this file with autoconf to produce a configure script.
 
 # Autoconf makes checking for and programming around assorted ancient
-# crap relatively painless.  But why bother?  Just rely on C89 and
-# POSIX, and when something breaks on some oddball machine, see
-# whether it's worth fixing.
+# crap relatively painless.  But why bother?  Just rely on POSIX, and
+# when something breaks on some oddball machine, see whether it's
+# worth fixing.
 
 AC_PREREQ(2.69)
 AC_INIT([Wolfpack Empire],

doc/coding

@@ -191,8 +191,6 @@ Do not use
 
 	// C++/C99 comments
 
-because they are not portable C89.
-
 Conditional compilation
 
 Unless the conditional code is very short, please comment it like
@@ -362,7 +360,7 @@ it's as relevant as ever:
 Portability
 -----------
 
-FIXME C89, POSIX
+FIXME C99, POSIX
 
 FIXME sizes, printf formats