patch 8.0.1826: configure uses old compiler flag

Problem:    Configure uses old compiler flag.
Solution:   Remove _DARWIN_C_SOURCE. (Kazunobu Kuriyama)
diff --git a/src/auto/configure b/src/auto/configure
index c1d477c..e65884c 100755
--- a/src/auto/configure
+++ b/src/auto/configure
@@ -4556,7 +4556,7 @@
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
   MACOS_X=yes
-  CPPFLAGS="$CPPFLAGS -D_DARWIN_C_SOURCE -DMACOS_X"
+  CPPFLAGS="$CPPFLAGS -DMACOS_X"
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking --disable-darwin argument" >&5
 $as_echo_n "checking --disable-darwin argument... " >&6; }
diff --git a/src/configure.ac b/src/configure.ac
index 7f55281..cfc3b1b 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -168,7 +168,7 @@
 if test "`(uname) 2>/dev/null`" = Darwin; then
   AC_MSG_RESULT(yes)
   MACOS_X=yes
-  CPPFLAGS="$CPPFLAGS -D_DARWIN_C_SOURCE -DMACOS_X"
+  CPPFLAGS="$CPPFLAGS -DMACOS_X"
 
   AC_MSG_CHECKING(--disable-darwin argument)
   AC_ARG_ENABLE(darwin,
diff --git a/src/version.c b/src/version.c
index 9743283..0348dc1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1826,
+/**/
     1825,
 /**/
     1824,