patch 8.2.3620: memory leak reported in libtlib

Problem:    Memory leak reported in libtlib.
Solution:   Call del_curterm() when cleaning up memory.  Rename term.h to
            termdefs.h to avoid a name clash.
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 572a41d..949b350 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -5,6 +5,7 @@
 void f_terminalprops(typval_T *argvars, typval_T *rettv);
 void set_color_count(int nr);
 int set_termname(char_u *term);
+void free_cur_term(void);
 void getlinecol(long *cp, long *rp);
 int add_termcap_entry(char_u *name, int force);
 int term_is_8bit(char_u *name);