Check for GNU libunistring and use it

Makefile.am

@@ -1,3 +1,4 @@
+ACLOCAL_AMFLAGS = -I m4
 
 sysconf_DATA = forked-daapd.conf
 

configure.in

@@ -1,6 +1,7 @@
 dnl Process this file with autoconf to produce a configure script.
 
 AC_INIT(config.h.in)
+AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_HEADER(config.h)
 AM_INIT_AUTOMAKE(forked-daapd, 0.11)
 
@@ -96,6 +97,12 @@ AC_ARG_WITH(oss4, AC_HELP_STRING([--with-oss4=includedir], [Use OSS4 with soundc
     esac ])
 
 dnl Checks for libraries.
+gl_LIBUNISTRING
+
+if test x$HAVE_LIBUNISTRING != xyes; then
+   AC_MSG_ERROR([GNU libunistring is required])
+fi
+
 PKG_CHECK_MODULES(ZLIB, [ zlib ])
 PKG_CHECK_MODULES(CONFUSE, [ libconfuse ])
 PKG_CHECK_MODULES(AVAHI, [ avahi-client >= 0.6.24 ])

m4/.gitignore

@@ -0,0 +1,3 @@
+libtool.m4
+lt*.m4
+

m4/libunistring.m4

@@ -0,0 +1,41 @@
+# libunistring.m4 serial 4
+dnl Copyright (C) 2009-2010 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl gl_LIBUNISTRING
+dnl Searches for an installed libunistring.
+dnl If found, it sets and AC_SUBSTs HAVE_LIBUNISTRING=yes and the LIBUNISTRING
+dnl and LTLIBUNISTRING variables and augments the CPPFLAGS variable, and
+dnl #defines HAVE_LIBUNISTRING to 1. Otherwise, it sets and AC_SUBSTs
+dnl HAVE_LIBUNISTRING=no and LIBUNISTRING and LTLIBUNISTRING to empty.
+
+AC_DEFUN([gl_LIBUNISTRING],
+[
+  dnl First, try to link without -liconv. libunistring often depends on
+  dnl libiconv, but we don't know (and often don't need to know) where
+  dnl libiconv is installed.
+  AC_LIB_HAVE_LINKFLAGS([unistring], [],
+    [#include <uniconv.h>], [u8_strconv_from_locale((char*)0);],
+    [no, consider installing GNU libunistring])
+  if test "$ac_cv_libunistring" != yes; then
+    dnl Second try, with -liconv.
+    AC_REQUIRE([AM_ICONV])
+    if test -n "$LIBICONV"; then
+      dnl We have to erase the cached result of the first AC_LIB_HAVE_LINKFLAGS
+      dnl invocation, otherwise the second one will not be run.
+      unset ac_cv_libunistring
+      glus_save_LIBS="$LIBS"
+      LIBS="$LIBS $LIBICONV"
+      AC_LIB_HAVE_LINKFLAGS([unistring], [],
+        [#include <uniconv.h>], [u8_strconv_from_locale((char*)0);],
+        [no, consider installing GNU libunistring])
+      if test -n "$LIBUNISTRING"; then
+        LIBUNISTRING="$LIBUNISTRING $LIBICONV"
+        LTLIBUNISTRING="$LTLIBUNISTRING $LTLIBICONV"
+      fi
+      LIBS="$glus_save_LIBS"
+    fi
+  fi
+])

src/Makefile.am

@@ -36,7 +36,7 @@ ANTLR_PRODUCTS =
 forked_daapd_CPPFLAGS = -D_GNU_SOURCE @ZLIB_CFLAGS@ @AVAHI_CFLAGS@ @SQLITE3_CFLAGS@ @FFMPEG_CFLAGS@ @CONFUSE_CFLAGS@ @TAGLIB_CFLAGS@ @MINIXML_CFLAGS@ @LIBPLIST_CFLAGS@ @LIBGCRYPT_CFLAGS@ @ALSA_CFLAGS@ @OSS4CPPFLAGS@ \
 	-DDATADIR="\"$(pkgdatadir)\"" -DCONFDIR="\"$(sysconfdir)\"" -DSTATEDIR="\"$(localstatedir)\""
 
-forked_daapd_LDADD = @ZLIB_LIBS@ @AVAHI_LIBS@ @SQLITE3_LIBS@ @FFMPEG_LIBS@ @CONFUSE_LIBS@ @FLAC_LIBS@ @TAGLIB_LIBS@ @LIBEVENT_LIBS@ @LIBAVL_LIBS@ @MINIXML_LIBS@ @ANTLR3C_LIBS@ @LIBPLIST_LIBS@ @LIBGCRYPT_LIBS@ @ALSA_LIBS@
+forked_daapd_LDADD = @ZLIB_LIBS@ @AVAHI_LIBS@ @SQLITE3_LIBS@ @FFMPEG_LIBS@ @CONFUSE_LIBS@ @FLAC_LIBS@ @TAGLIB_LIBS@ @LIBEVENT_LIBS@ @LIBAVL_LIBS@ @MINIXML_LIBS@ @ANTLR3C_LIBS@ @LIBPLIST_LIBS@ @LIBGCRYPT_LIBS@ @ALSA_LIBS@ @LIBUNISTRING@
 forked_daapd_SOURCES = main.c \
 	db.c db.h \
 	logger.c logger.h \