configure: use the proper '=' POSIX shell operator

The '==' shell operator doesn't work in POSIX shells, so when sh is
symlinked to a POSIX shell such as dash and not a bash shell, the
configure tests that use this operator fail to work.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Index: sconeserver-211/configure.in
===================================================================
--- sconeserver-211.orig/configure.in	2013-05-14 12:00:19.000000000 +0200
+++ sconeserver-211/configure.in	2013-06-16 18:47:31.000000000 +0200
@@ -121,7 +121,7 @@
   [SSL="$withval"],
   [AC_CHECK_HEADER([openssl/ssl.h],[SSL="yes"],[SSL="no"])]
 )
-if test "x$SSL" == "xyes"; then
+if test "x$SSL" = "xyes"; then
   AC_CHECK_HEADER([openssl/ssl.h],,
     [AC_MSG_ERROR([header file <openssl/ssl.h> is required for OpenSSL, use --with-openssl-path=PATH])]
   )
@@ -179,7 +179,7 @@
 )
 
 # Check we have libxml2 if Sconesite is enabled
-if test "x$SCONESITE" == "xyes"; then
+if test "x$SCONESITE" = "xyes"; then
   if test "x$ac_cv_lib_xml2_xmlNewDoc" != "xyes"; then
     AC_MSG_ERROR([library 'libxml2' is required for Sconesite])
   fi
@@ -195,7 +195,7 @@
   [MAGICK_CONFIG="Magick++-config"]
 )
 AC_CHECK_PROG([MAGICK], ["$MAGICK_CONFIG"], [yes], [no])
-if test "x$MAGICK" == "xyes"; then
+if test "x$MAGICK" = "xyes"; then
   MAGICK_CFLAGS=`$MAGICK_CONFIG --cppflags`
   MAGICK_LDFLAGS=`$MAGICK_CONFIG --ldflags`
   MAGICK_LIBS=`$MAGICK_CONFIG --libs`
@@ -209,7 +209,7 @@
 )
 
 # Need ImageMagick for image
-if test "x$IMAGE" == "xyes"; then
+if test "x$IMAGE" = "xyes"; then
   if test "x$MAGICK" != "xyes"; then
     AC_MSG_ERROR([library 'Magick++' is required for image])
   fi
@@ -227,7 +227,7 @@
   [RSS="yes"]
 )
 # Need libxml2 library for rss
-if test "x$RSS" == "xyes"; then
+if test "x$RSS" = "xyes"; then
   if test "x$ac_cv_lib_xml2_xmlNewDoc" != "xyes"; then
     AC_MSG_ERROR([library 'libxml2' is required for the rss module])
   fi
@@ -249,7 +249,7 @@
   [AC_CHECK_HEADER([mysql/mysql.h],[MYSQL="yes"],[MYSQL="no"])]
 )
 # Need mysqlclient library for mysql
-if test "x$MYSQL" == "xyes"; then
+if test "x$MYSQL" = "xyes"; then
   AC_CHECK_LIB([mysqlclient],[mysql_init],
     [CXXFLAGS="$CXXFLAGS `$MYSQL_CONFIG --cflags`"
      MYSQL_LIBADD=`$MYSQL_CONFIG --libs`
@@ -266,7 +266,7 @@
   [AC_CHECK_HEADER([sqlite3.h],[SQLITE="yes"],[SQLITE="no"])]
 )
 # Need sqlite3 library for sqlite
-if test "x$SQLITE" == "xyes"; then
+if test "x$SQLITE" = "xyes"; then
   AC_CHECK_LIB([sqlite3],[sqlite3_open_v2],
     [SQLITE_LIBADD="-lsqlite3"
      AC_SUBST(SQLITE_LIBADD)],
@@ -283,7 +283,7 @@
   [AC_CHECK_HEADER([mpfr.h],[MATHS="yes"],[MATHS="no"])]
 )
 # Need libgmp and libmpfr library for maths
-if test "x$MATHS" == "xyes"; then
+if test "x$MATHS" = "xyes"; then
   AC_CHECK_LIB([mpfr],[mpfr_init],
     [MATHS_LIBADD="-lgmp -lmpfr"
      AC_SUBST(MATHS_LIBADD)],
@@ -300,7 +300,7 @@
   [AC_CHECK_HEADER([X11/Xlib.h],[UI="yes"],[UI="no"])]
 )
 # Need libX11 library for ui
-if test "x$UI" == "xyes"; then
+if test "x$UI" = "xyes"; then
   AC_CHECK_LIB([X11],[XOpenDisplay],
     [UI_LIBADD="-lX11"
      AC_SUBST(UI_LIBADD)],