docs: adjust for the changed name of the header-file package on Debian

Also, be more complete, reword a few things, and stop mentioning Slang.

README

@@ -25,7 +25,7 @@ Overview
 
 How to compile and install nano
 
-    Download the latest nano source tarball, then:
+    Download the latest nano source tarball, and then:
 
         tar -xvf nano-x.y.tar.gz
         cd nano-x.y
@@ -33,12 +33,13 @@ How to compile and install nano
         make
         make install
 
-    It's that simple.  Use --prefix with configure to override the
-    default installation directory of /usr/local.
+    You will need the header files of ncurses installed for ./configure
+    to succeed -- get them from libncurses-dev (Debian) or ncurses-devel
+    (Fedora) or a similarly named package.  Use --prefix with ./configure
+    to override the default installation directory of /usr/local.
 
-    If you haven't configured with the --disable-nanorc option, after
-    installation you may want to copy the doc/sample.nanorc file to
-    your home directory, rename it to ".nanorc", and then edit it
+    After installation you may want to copy the doc/sample.nanorc file
+    to your home directory, rename it to ".nanorc", and then edit it
     according to your taste.
 
 Web Page
@@ -51,8 +52,10 @@ Mailing Lists
 
     + info-nano@gnu.org is a very low traffic list used to announce
       new nano versions or other important info about the project.
+
     + help-nano@gnu.org is for those seeking to get help without
       wanting to hear about the technical details of its development.
+
     + nano-devel@gnu.org is the list used by the people that make nano
       and a general development discussion list, with moderate traffic.
 

README.GIT

@@ -22,11 +22,11 @@ packages:
 - pkg-config  (version >= 0.22)
 - texinfo     (version >= 4.0)
 
-If you want UTF-8 support, you will also need libncursesw5-dev installed
-(version >= 5.7), or libslang2-dev (version >= 2.0) if you use --with-slang.
+You will also need to have the header files for ncurses installed,
+from libncurses-dev on Debian, ncurses-devel on Fedora, or similar.
 
-These should all be available in your distro's package manager or software
-center, or otherwise on any GNU mirror.
+These should all be available in your distro's package manager or
+software center, or otherwise on any GNU mirror.
 
 
 Download the source

configure.ac

@@ -608,7 +608,7 @@ fi
 if eval "test x$CURSES_LIB_NAME = x"; then
 	AC_MSG_ERROR([
   *** No curses lib was found.  Please install the curses header files
-  *** from libncursesw5-dev (Debian), ncurses-devel (Fedora), or similar.
+  *** from libncurses-dev (Debian), ncurses-devel (Fedora), or similar.
   *** (Or install ncurses from https://ftp.gnu.org/gnu/ncurses/.)])
 else
 	AC_MSG_RESULT([  The curses library to be used is: $CURSES_LIB_NAME])