patch 8.2.4457: the GPM library can only be linked statically

Problem:    The GPM library can only be linked statically.
Solution:   Make it possible to load the GPM library dynamically. (Damien)
diff --git a/src/version.c b/src/version.c
index 0bd4991..85af241 100644
--- a/src/version.c
+++ b/src/version.c
@@ -375,7 +375,11 @@
 	"-mouse_dec",
 # endif
 # ifdef FEAT_MOUSE_GPM
+#  ifdef DYNAMIC_GPM
+	"+mouse_gpm/dyn",
+#  else
 	"+mouse_gpm",
+#  endif
 # else
 	"-mouse_gpm",
 # endif
@@ -751,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4457,
+/**/
     4456,
 /**/
     4455,