README: Fix spelling Red Hat. Remove unneeded references to Debian

and Red Hat.  Document the use of libxml2 as a weak prerequisite.

README

@@ -70,7 +70,7 @@ Supported file systems:
 
 Basic requirements:
   You need to have the X11 development include files installed
-  (called xlib6g-dev in Debian and XFree86-devel in RedHat).
+  (called xlib6g-dev in Debian and XFree86-devel in Red Hat).
 
 Build tool requirements:
   On x86 Systems gcc >= 2.7.2 is required.
@@ -81,12 +81,12 @@ Build tool requirements:
 
   Of course you also need "make" (most likely GNU make).
 
-  You also need flex version 2.5 or later and bison.  If you are
-  using RedHat or Debian, install the flex and bison packages.
+  You also need flex version 2.5 or later and bison.
 
 Optional support libraries:
   If you want CUPS printing support, please install both cups and cups-devel
   packages.
+  Install the libxml2 package to get a functional msxml implementation.
 
 4. COMPILATION