patch 8.1.2062: the mouse code is spread out

Problem:    The mouse code is spread out.
Solution:   Move all the mouse code to mouse.c. (Yegappan Lakshmanan,
            closes #4959)
diff --git a/src/configure.ac b/src/configure.ac
index f7a71d0..97753a6 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -2106,7 +2106,7 @@
   AC_DEFINE(FEAT_TERMINAL)
   TERM_SRC="libvterm/src/encoding.c libvterm/src/keyboard.c libvterm/src/mouse.c libvterm/src/parser.c libvterm/src/pen.c libvterm/src/termscreen.c libvterm/src/state.c libvterm/src/unicode.c libvterm/src/vterm.c"
   AC_SUBST(TERM_SRC)
-  TERM_OBJ="objects/encoding.o objects/keyboard.o objects/mouse.o objects/parser.o objects/pen.o objects/termscreen.o objects/state.o objects/unicode.o objects/vterm.o"
+  TERM_OBJ="objects/encoding.o objects/keyboard.o objects/termmouse.o objects/parser.o objects/pen.o objects/termscreen.o objects/state.o objects/unicode.o objects/vterm.o"
   AC_SUBST(TERM_OBJ)
 fi