autoconf: fix getaddrinfo checking errors on mingw

`AC_CHECK_FUNCS` can not properly check `getaddrinfo` because this
function requires some special headers on mingw.
Using `AC_CHECK_DECL` can effectively solve this issue.

Same for
- getnameinfo
- getprotobynumber
- getservbyname
- inet_ntop
- inet_pton

(cherry picked from commit 6d54be2cc078351b4ce1e469bedc4a976f4e3636)

configure.ac

@@ -251,6 +251,7 @@ AC_CHECK_HEADERS([ \
   sys/wait.h \
   sys/random.h \
   errno.h \
+  afunix.h \
 ])
 
 case "${host_os}" in
@@ -347,7 +348,7 @@ AM_CONDITIONAL(BUILD_MIDIPIX, test x$midipix = xtrue)
 AM_CONDITIONAL(BUILD_WITH_NO_UNDEFINED, test x$bwin32 = xtrue || test x$cygwin = xtrue || test x$midipix = xtrue)
 
 if test x$bwin32 = xtrue; then
-   AC_SEARCH_LIBS([getservbyname],[ws2_32])
+  AC_HAVE_LIBRARY([ws2_32])
 fi
 
 dnl Checks for typedefs, structures, and compiler characteristics.
@@ -367,11 +368,7 @@ AC_CHECK_FUNCS([ \
   getegid \
   geteuid \
   getifaddrs \
-  getnameinfo \
-  getprotobynumber \
   gettimeofday \
-  inet_ntop \
-  inet_pton \
   issetugid \
   mach_absolute_time \
   mmap \
@@ -395,17 +392,36 @@ AC_CHECK_FUNCS([ \
   unsetenv \
   usleep \
   vasprintf \
-  getservbyname \
   getrandom \
 ])
 
-AC_CHECK_FUNCS(_gmtime64_s, [have__gmtime64_s=yes], )
-if test "x$have__gmtime64_s" != "xyes"; then
-  AC_CHECK_FUNCS(_gmtime64)
-fi
+AS_IF([test x$bwin32 = xtrue],
+  AC_CHECK_FUNCS(_gmtime64_s, , [AC_CHECK_FUNCS(_gmtime64)])
+)
 
 AM_CONDITIONAL(STRLCPY_IMPL, [test x"$ac_cv_func_strlcpy" = xno])
 
+m4_define([funcstochk],
+  [getnameinfo
+  getprotobynumber
+  getservbyname
+  inet_ntop
+  inet_pton]
+)
+
+AS_IF([test x$bwin32 = xtrue],
+  [AX_CHECK_DECLS_EX([funcstochk getaddrinfo],
+    [#ifdef _WIN32
+    #include <winsock2.h>
+    #include <ws2tcpip.h>
+    #endif])],
+  [AC_CHECK_FUNCS(m4_normalize(funcstochk))]
+)
+
+m4_undefine([funcstochk])
+
+dnl check getaddrinfo and gethostbyname_r for non-windows
+AS_IF([test x$bwin32 = xfalse], [
 AC_CACHE_CHECK(
     [for getaddrinfo],
     [libevent_cv_getaddrinfo],
@@ -485,6 +501,7 @@ AC_CHECK_FUNC(gethostbyname_r, [
 ])
 
 fi
+]) dnl end of checking getaddrinfo and gethostbyname_r
 
 AC_MSG_CHECKING(for F_SETFD in fcntl.h)
 AC_EGREP_CPP(yes,
@@ -738,6 +755,9 @@ AC_CHECK_TYPES([struct linger],,,
 #ifdef HAVE_SYS_SOCKET_H
 #include <sys/socket.h>
 #endif
+#ifdef _WIN32
+#include <winsock2.h>
+#endif
 ])
 
 AC_MSG_CHECKING([for socklen_t])

m4/ax_check_funcs_ex.m4

@@ -0,0 +1,22 @@
+# Check if the function is available.
+# HAVE_XXX will be defined if yes.
+
+# $1: the name of function
+# $2: the headers in where the function declared
+AC_DEFUN([AX_CHECK_DECL_EX], [dnl
+	AS_IF([test "x$2" = "x"], [AC_MSG_ERROR([header not privided])])
+	AS_VAR_PUSHDEF([have_func_var], [HAVE_[]m4_toupper($1)])
+	AC_CHECK_DECL([$1],dnl
+		[AC_DEFINE([have_func_var], [1], [Define to 1 if you have the `$1' function.])],,dnl
+		[$2]dnl
+	)
+	AS_VAR_POPDEF([have_func_var])dnl
+])
+
+AC_DEFUN([AX_CHECK_DECLS_EX], [dnl
+	AS_IF([test "x$2" = "x"], [AC_MSG_ERROR([header not privided])])
+	m4_foreach([decl],dnl
+		m4_split(m4_normalize($1)),dnl
+		[AX_CHECK_DECL_EX([decl], [$2])]dnl
+	)
+])