Adjust to Autoconf-2.71

Autoconf-2.71 miconverts:

    AC_CHECK_FUNCS( \
      strcpy \
      strdup \
      strchr \
      strlen \
      strcat \
      strtok \
    )

into:

    for ac_func in strcpy strdup strchr \ strlen \ strcat \ strtok \
    do :
      [...]
    done

According to Autoconf documentation, the AC_CHECK_FUNCS supports
new lines as tokenizers.

This patch works around this issue by not escaping the new lines.

<https://bugzilla.redhat.com/show_bug.cgi?id=1999491>
<https://savannah.gnu.org/support/index.php?110571>

Author: ppisar

configure.ac

@@ -171,13 +171,13 @@ AC_TYPE_UID_T
 # Checks for library functions.
 ##
 AC_FUNC_MALLOC
-AC_CHECK_FUNCS( \
-  strcpy \
-  strdup \
-  strchr \ 
-  strlen \ 
-  strcat \ 
-  strtok \ 
+AC_CHECK_FUNCS(
+  strcpy
+  strdup
+  strchr
+  strlen
+  strcat
+  strtok
 )
 AC_CHECK_FUNCS([getopt_long])