patch 8.0.1309: cannot use 'balloonexpr' in a terminal

Problem:    Cannot use 'balloonexpr' in a terminal.
Solution:   Add 'balloonevalterm' and add code to handle mouse movements in a
            terminal. Initial implementation for Unix with GUI.
diff --git a/src/misc1.c b/src/misc1.c
index f33fd3b..4c691bb 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -3345,6 +3345,7 @@
 	|| c == K_LEFTDRAG
 	|| c == K_LEFTRELEASE
 	|| c == K_LEFTRELEASE_NM
+	|| c == K_MOUSEMOVE
 	|| c == K_MIDDLEMOUSE
 	|| c == K_MIDDLEDRAG
 	|| c == K_MIDDLERELEASE