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/Makefile b/src/Makefile
index 8b0b268..24d39e8 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -526,6 +526,8 @@
 # though you have gpm libraries and includes.
 # For Debian/Ubuntu gpm support requires the libgpm-dev package.
 #CONF_OPT_GPM = --disable-gpm
+# Use this to enable dynamic loading of the GPM library.
+#CONF_OPT_GPM = --enable-gpm=dynamic
 
 # sysmouse - For mouse support on FreeBSD and DragonFly console via sysmouse
 # Uncomment this when you do not want do include sysmouse support, even