configure: make sure to fail if no CXX is found

src/configure.ac

@@ -10,9 +10,17 @@ LT_INIT
 AC_CONFIG_MACRO_DIR([m4])
 
 AC_PROG_CXX
+# AC_PROG_CXX used to set CXX to C when no compiler was found, but now it's
+# g++. So actually try to build a program to verify the compiler.
 if test C$CXX = C ; then
    AC_MSG_ERROR([C++ compiler needed. Please install one (ie: gnu g++)])
 fi
+AC_LANG_PUSH([C++])
+AC_TRY_LINK([],[], rcl_link_ok=yes, rcl_link_ok=no)
+if test "$rcl_link_ok" = "no" ; then
+   AC_MSG_ERROR([No working C++ compiler was found])
+fi
+AC_LANG_POP([C++])
 
 AC_PROG_YACC
 

website/pages/recoll-windows.txt

@@ -3,7 +3,7 @@ Jean-Francois Dockes <jf at dockes.org>
 :date:
 
 :recollversion: 1.23.0-2017-01-07-78b8ad
-:windir: downwin-adb3c
+:windir: downwin-c67b5
 
 image:recoll-windows10-thumb.png[link="recoll-windows10.png"]
 
@@ -35,13 +35,6 @@ files which would take space for nothing otherwise.
 
 == Installation
 
-- Download the 
-  http://www.recoll.org/downloads/{windir}/recoll-setup-{recollversion}.exe[Recoll
-  setup file].
-
-- Execute the setup file. This is a vanilla installer generated by Inno
-  Setup, and it will ask the usual questions.
-
 - Download and install Python 2.7.10 or 2.7.11 (e.g.
   https://www.python.org/ftp/python/2.7.11/python-2.7.11.msi[Python
   2.7.11]). Recoll currently does not work with Python3. *_On the
@@ -51,6 +44,13 @@ files which would take space for nothing otherwise.
   http://www.7-zip.org/. This is only useful if you need to index files
   compressed with Unix methods (not needed for zip files).
 
+- Download the 
+  http://www.recoll.org/downloads/{windir}/recoll-setup-{recollversion}.exe[Recoll
+  setup file].
+
+- Execute the setup file. This is a vanilla installer generated by Inno
+  Setup, and it will ask the usual questions.
+
 //NOTE: The installer needs administrator rights in order to install to
 //`C:\Program Files`. If you want to install on a machine where you have no
 //administrator rights, you can use the