daemon: Use pkg-config to locate Augeas CFLAGS / libraries.

Augeas 0.10 depends on libxml2, so this is now required in the
appliance (in fact, it was already present).

However this exposed two bugs:

(1) In libguestfs we use a home-brewed recipe for Augeas flags,
resulting in this error:
/usr/include/augeas.h:24:25: fatal error: libxml/tree.h: No such file or directory

(2) Augeas's own augeas.pc didn't include the libxml2 flags, so
it was broken.  This requires a patch to Augeas 0.10, see:
https://www.redhat.com/archives/augeas-devel/2011-December/msg00008.html

Change to using pkg-config to detect Augeas.  It is still an optional
library.

appliance/packagelist.in

@@ -105,6 +105,7 @@ gawk
 grep
 gzip
 jfsutils
+libxml2
 lsof
 lvm2
 lzop

configure.ac

@@ -315,22 +315,19 @@ AC_CHECK_LIB([portablexdr],[xdrmem_create],[],[
         AC_SEARCH_LIBS([xdrmem_create],[rpc xdr nsl])
         ])
 
-dnl Check for Augeas (now optional).
-AC_CHECK_LIB([augeas],[aug_match],[
-        have_augeas=yes
-        AUGEAS_LIB="-laugeas"
+dnl Check for Augeas (optional).
+PKG_CHECK_MODULES([AUGEAS], [augeas],
+        [AC_SUBST([AUGEAS_CFLAGS])
+         AC_SUBST([AUGEAS_LIBS])
+         AC_DEFINE([HAVE_AUGEAS],[1],[Define to 1 if you have Augeas])
 
-        old_LIBS="$LIBS"
-        LIBS="$LIBS $AUGEAS_LIB"
-        dnl Check for functions not available in earlier versions of Augeas.
-        AC_CHECK_FUNCS([aug_load aug_defvar aug_defnode])
-        LIBS="$old_LIBS"
-
-        ],[have_augeas=no])
-if test "x$have_augeas" = "xyes"; then
-        AC_DEFINE([HAVE_AUGEAS],[1],[Define to 1 if you have Augeas])
-fi
-AC_SUBST([AUGEAS_LIB])
+         old_LIBS="$LIBS"
+         LIBS="$LIBS $AUGEAS_LIBS"
+         dnl Check for functions not available in earlier versions of Augeas.
+         AC_CHECK_FUNCS([aug_load aug_defvar aug_defnode])
+         LIBS="$old_LIBS"
+        ],
+        [AC_MSG_WARN([augeas not found, some core features will be disabled])])
 
 dnl Check for libselinux (optional).
 AC_CHECK_HEADERS([selinux/selinux.h])

daemon/Makefile.am

@@ -166,7 +166,7 @@ guestfsd_LDADD = \
 	liberrnostring.a \
 	libprotocol.a \
 	$(SELINUX_LIB) \
-	$(AUGEAS_LIB) \
+	$(AUGEAS_LIBS) \
 	$(top_builddir)/gnulib/lib/.libs/libgnu.a \
 	$(GETADDRINFO_LIB) \
 	$(HOSTENT_LIB) \
@@ -177,6 +177,6 @@ guestfsd_LDADD = \
 	$(SERVENT_LIB)
 
 guestfsd_CPPFLAGS = -I$(top_srcdir)/gnulib/lib -I$(top_builddir)/gnulib/lib
-guestfsd_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
+guestfsd_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS) $(AUGEAS_CFLAGS)
 
 .PHONY: force