patch 8.2.3796: the funcexe_T struct members are not named consistently

Problem:    The funcexe_T struct members are not named consistently.
Solution:   Prefix "fe_" to all the members.
diff --git a/src/terminal.c b/src/terminal.c
index 7e2f45b..f584200 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -4334,9 +4334,9 @@
     argvars[0].vval.v_number = term->tl_buffer->b_fnum;
     argvars[1] = item->li_next->li_tv;
     CLEAR_FIELD(funcexe);
-    funcexe.firstline = 1L;
-    funcexe.lastline = 1L;
-    funcexe.evaluate = TRUE;
+    funcexe.fe_firstline = 1L;
+    funcexe.fe_lastline = 1L;
+    funcexe.fe_evaluate = TRUE;
     if (call_func(func, -1, &rettv, 2, argvars, &funcexe) == OK)
     {
 	clear_tv(&rettv);