patch 8.0.0952: has('terminal') does not check existence of dll file

Problem:    MS-Windows: has('terminal') does not check existence of dll file.
Solution:   Check if the winpty dll file can be loaded. (Ken Takata)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 4521835..c85c334 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -5926,7 +5926,7 @@
 #ifdef FEAT_TERMGUICOLORS
 	"termguicolors",
 #endif
-#ifdef FEAT_TERMINAL
+#if defined(FEAT_TERMINAL) && !defined(WIN3264)
 	"terminal",
 #endif
 #ifdef TERMINFO
@@ -6134,6 +6134,10 @@
 	else if (STRICMP(name, "netbeans_enabled") == 0)
 	    n = netbeans_active();
 #endif
+#if defined(FEAT_TERMINAL) && defined(WIN3264)
+	else if (STRICMP(name, "terminal") == 0)
+	    n = terminal_enabled();
+#endif
     }
 
     rettv->vval.v_number = n;