patch 8.0.1132: #if condition is not portable

Problem:    #if condition is not portable.
Solution:   Add defined(). (Zuloloxi, closes #2136)
diff --git a/src/libvterm/src/vterm.c b/src/libvterm/src/vterm.c
index b2a7240..1789fb3 100644
--- a/src/libvterm/src/vterm.c
+++ b/src/libvterm/src/vterm.c
@@ -130,7 +130,8 @@
   return vt->outbuffer_cur >= vt->outbuffer_len - 1;
 }
 
-#if _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE || _BSD_SOURCE
+#if (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 500) \
+	|| defined(_ISOC99_SOURCE) || defined(_BSD_SOURCE)
 # undef VSNPRINTF
 # define VSNPRINTF vsnprintf
 #else
diff --git a/src/version.c b/src/version.c
index 1ff5b3e..b90665e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1132,
+/**/
     1131,
 /**/
     1130,