AC_CHECK_HEADERS_ONCE() is very special cannot be conditionalized.

Use plain AC_CHECK_HEADERS() instead, so ./configure will not check
for magic.h and zlib.h when --disable-libmagic is given.
Patch by Christian Weisgerber.


git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@5505 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

ChangeLog

-2015-12-22 Benno Schulenberg  <bensberg@justemail.net>
+2015-12-23  Christian Weisgerber  <naddy@mips.inka.de>
+	* configure.ac: AC_CHECK_HEADERS_ONCE() is very special and cannot be
+	conditionalized.  Use plain AC_CHECK_HEADERS() instead, to not check
+	for magic.h and zlib.h when configuring with --disable-libmagic.
+
+2015-12-22  Benno Schulenberg  <bensberg@justemail.net>
 	* src/color.c (precalc_multicolorinfo, alloc_multidata_if_needed):
 	Move these two functions to the file where they belong.  And make
 	the checking for an impatient user into a separate routine.

configure.ac

@@ -657,9 +657,9 @@ AC_MSG_RESULT(no),
 AC_MSG_WARN([*** Can't check for macro redefinability when cross-compiling]))
 
 AS_IF([test "x$enable_libmagic" != "xno"], [
-  AC_CHECK_HEADERS_ONCE([magic.h])
+  AC_CHECK_HEADERS([magic.h])
   AC_CHECK_LIB(magic, magic_open)
-  AC_CHECK_HEADERS_ONCE([zlib.h])
+  AC_CHECK_HEADERS([zlib.h])
   AC_CHECK_LIB(z, inflate)
 ])