fixed detecting libevent v1 if libevent v2 is not available

configure

@@ -11169,6 +11169,16 @@ _ACEOF
 ;;
   esac
 
+ac_fn_c_check_type "$LINENO" "u_char" "ac_cv_type_u_char" "$ac_includes_default"
+if test "x$ac_cv_type_u_char" = xyes; then :
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_U_CHAR 1
+_ACEOF
+
+
+fi
+
 
 getdns_LIBS=$LIBS
 getdns_LDFLAGS=$LDFLAGS
@@ -11268,8 +11278,23 @@ _ACEOF
  have_libevent=1
                 EXTENSION_LIBEVENT_EXT_LIBS="$ac_cv_search_event_loop"
 else
-  as_fn_error $? "event2/event.h missing, try without libevent" "$LINENO" 5
-                have_libevent=0
+  for ac_header in event.h
+do :
+  ac_fn_c_check_header_compile "$LINENO" "event.h" "ac_cv_header_event_h" "$ac_includes_default
+"
+if test "x$ac_cv_header_event_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_EVENT_H 1
+_ACEOF
+ have_libevent=1
+                    EXTENSION_LIBEVENT_EXT_LIBS="$ac_cv_search_event_loop"
+else
+  as_fn_error $? "event2/event.h and event.h missing, try without libevent" "$LINENO" 5
+                    have_libevent=0
+fi
+
+done
+
 fi
 
 done

configure.ac

@@ -189,6 +189,7 @@ AC_TYPE_UINT16_T
 AC_TYPE_UINT32_T
 AC_TYPE_UINT64_T
 AC_TYPE_UINT8_T
+AC_CHECK_TYPES([u_char])
 
 getdns_LIBS=$LIBS
 getdns_LDFLAGS=$LDFLAGS
@@ -213,8 +214,12 @@ AS_IF([test x_$withval = x_no],
             [AC_CHECK_HEADERS([event2/event.h],
                 [have_libevent=1]
                 [EXTENSION_LIBEVENT_EXT_LIBS="$ac_cv_search_event_loop"],
-                [AC_MSG_ERROR([event2/event.h missing, try without libevent])]
-                [have_libevent=0],
+                [AC_CHECK_HEADERS([event.h],
+                    [have_libevent=1]
+                    [EXTENSION_LIBEVENT_EXT_LIBS="$ac_cv_search_event_loop"],
+                    [AC_MSG_ERROR([event2/event.h and event.h missing, try without libevent])]
+                    [have_libevent=0],
+                    [AC_INCLUDES_DEFAULT])],
                 [AC_INCLUDES_DEFAULT])],
                 [AC_MSG_ERROR([libevent missing, try without libevent])]
             )],

src/config.h.in

@@ -12,6 +12,9 @@
 /* Define to 1 if you have the `event_base_new' function. */
 #undef HAVE_EVENT_BASE_NEW
 
+/* Define to 1 if you have the <event.h> header file. */
+#undef HAVE_EVENT_H
+
 /* Define to 1 if you have the <ev.h> header file. */
 #undef HAVE_EV_H
 
@@ -57,6 +60,9 @@
 /* Define to 1 if you have the <uv.h> header file. */
 #undef HAVE_UV_H
 
+/* Define to 1 if the system has the type `u_char'. */
+#undef HAVE_U_CHAR
+
 /* Define to the sub-directory in which libtool stores uninstalled libraries.
    */
 #undef LT_OBJDIR

src/example/getdns_libevent.h

@@ -27,10 +27,11 @@
 #include <getdns/getdns.h>
 #include <getdns/getdns_ext_libevent.h>
 #ifdef HAVE_EVENT2_EVENT_H
-#include <event2/event.h>
+    #include <event2/event.h>
 #else
-#  ifndef u_char
-#    define u_char unsigned char
-#  endif
-#include <event.h>
+    #include <event.h>
+#endif
+
+#ifndef HAVE_U_CHAR
+    typedef unsigned char u_char;
 #endif