Add strndupa.h to distribution and update README

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Makefile.am

@@ -2,7 +2,7 @@ ACLOCAL_AMFLAGS     = -I m4
 
 lib_LTLIBRARIES     = libite.la
 pkgincludedir       = $(includedir)/lite
-pkginclude_HEADERS  = lite.h queue.h conio.h tree.h strlite.h strdupa.h
+pkginclude_HEADERS  = lite.h queue.h conio.h tree.h strlite.h strdupa.h strndupa.h
 libite_la_SOURCES   = chomp.c copyfile.c dir.c fexist.c fisdir.c fmode.c fparseln.c	\
 		      fsendfile.c ifconfig.c lfile.c makepath.c pidfile.c pidfilefn.c	\
 		      progress.c reallocarray.c rsync.c strlcpy.c strlcat.c strtonum.c	\

README.md

@@ -290,7 +290,11 @@ some other platforms.
 
 - `strdupa(str)`
 
-  http://man7.org/linux/man-pages/man3/strdup.3.html
+  http://man7.org/linux/man-pages/man3/strdupa.3.html
+
+- `strndupa(str)`
+
+  http://man7.org/linux/man-pages/man3/strndupa.3.html
 
 
 OpenBSD/NetBSD/FreeBSD Functions