no AC_LANG_SOURCE call detected in body

[Bruce Korb]

I was trying to chase down some still-hanging-around warnings.
This warning is insufficiently clear because I *do* have AC_LANG_SOURCE:

configure.ac:139: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call detected in 
body
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2662: _AC_LINK_IFELSE is expanded from...
../../lib/autoconf/general.m4:2679: AC_LINK_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:606: AS_IF is expanded from...
../../lib/autoconf/general.m4:2032: AC_CACHE_VAL is expanded from...
config/ag_macros.m4:347: AG_WITHLIB_XML2 is expanded from...
config/ag_macros.m4:674: INVOKE_AG_MACROS is expanded from...
configure.ac:139: the top level


    348 AC_DEFUN([AG_WITHLIB_XML2],[
[........]
    422   AC_MSG_CHECKING([whether libxml2 can be linked with])
    423   AC_CACHE_VAL([ag_cv_with_libxml2],[
    424   AC_LINK_IFELSE(
    425     [AC_LANG_SOURCE(address@hidden:@include <libxml/parser.h>
    426 @%:@include <libxml/tree.h>
    427
    428 int main () {
    429 xmlDocPtr p = xmlParseFile( "mumble.xml" ); }]])],
    430     [ag_cv_with_libxml2=yes],
    431     [ag_cv_with_libxml2=no]) # end of AC_LINK_IFELSE
    432   ]) # end of AC_CACHE_VAL for ag_cv_with_libxml2