Writing Elbereth's name and walking around it segfaults the game

This is a bug that exists in both bingehack4 and our upstream nethack4. It appears to be due to a flaw in the pline/vpline code.

Bingehack4 commit: `85dbdba39459cb83fc0010010daed47a86718c2b`
Nethack4 commit: `cb7da80ab47cfe158b0a32b7e47f36b2ab6c529b`

It can be reproduced with the following steps:

1. Create a new (or load an existing game)
2. Write Elbereth's name 50 times `50^e`
3. Move to an adjacent space
4. Write Elbereth's name 50 times `50^e`
5. Move back and forth between the two spaces (I usually experience a segfault around the 7th move)

The stacktrace of the segfault itself isn't particularly interesting. It just occurs when `histevents[0]` is out of range. However the stacktrace of where `histcount` is changed to an unrealistic value is fairly interesting. Here's the stacktrace of that situation where `histcount` changed from 54 to 1164473445 (in the original game that I found this issue during).

```
#0 0x00007f414c171b3e in __strcpy_ssse3 () from /usr/lib/libc.so.6
#1 0x00007f414e5b83d2 in vpline (nonblocking=nonblocking@entry=0 '\000', norepeat=norepeat@entry=0 '\000',
line=0x562f4a103c90 "You read: \"Elbe? ??E||er? nF||cretnEl|? et?Llbcre?nE|b rethv|be?eth_lberethEl e?ct\\ElUerc+h|l erc?h|l|?reth4|berethL?? rcth?l|e?e??Elbere?h||bc?e?hElberTth[|ber?thElbereth l|e(e?nEl crcthE|b?rethFlb7r"..., line@entry=0x7f414e6b63bd "You %s: \"%s\".", the_args=the_args@entry=0x7ffea3a8e8e0) at /home/loothelion/repos/bingehack4/libnethack/src/pline.c:99
#2 0x00007f414e5b84d0 in pline (line=line@entry=0x7f414e6b63bd "You %s: \"%s\".") at /home/loothelion/repos/bingehack4/libnethack/src/pline.c:33
#3 0x00007f414e5ee15a in read_engr_at (x=37, y=13) at /home/loothelion/repos/bingehack4/libnethack/src/engrave.c:376
#4 0x00007f414e56bbb5 in look_here (obj_cnt=8, picked_some=, show_weight=show_weight@entry=0 '\000', feeling=0 '\000') at /home/loothelion/repos/bingehack4/libnethack/src/invent.c:2004
#5 0x00007f414e5a7396 in check_here (picked_some=) at /home/loothelion/repos/bingehack4/libnethack/src/pickup.c:71
#6 0x00007f414e5aa35d in pickup (what=what@entry=1, uim=) at /home/loothelion/repos/bingehack4/libnethack/src/pickup.c:292
#7 0x00007f414e578bbe in spoteffects (pick=, pick@entry=1 '\001') at /home/loothelion/repos/bingehack4/libnethack/src/hack.c:2349
#8 0x00007f414e57ce7f in domove (arg=, uim=, thismove=) at /home/loothelion/repos/bingehack4/libnethack/src/hack.c:2241
#9 0x00007f414e54c555 in do_command (command=, command@entry=79, arg=arg@entry=0x7ffea3a8ed18) at /home/loothelion/repos/bingehack4/libnethack/src/cmd.c:1663
#10 0x00007f414e5425bb in command_input (cmdidx=cmdidx@entry=79, arg=arg@entry=0x7ffea3a8ed18) at /home/loothelion/repos/bingehack4/libnethack/src/allmain.c:1402
#11 0x00007f414e546b46 in nh_play_game (fd=fd@entry=6, followmode=, followmode@entry=FM_PLAY) at /home/loothelion/repos/bingehack4/libnethack/src/allmain.c:660
#12 0x00007f414d31317d in nhnet_play_game (gid=6, followmode=FM_PLAY) at /home/loothelion/repos/bingehack4/libnethack_client/src/clientapi.c:158
#13 0x0000562f47ffc52c in playgame (fd_or_gameno=6, followmode=) at /home/loothelion/repos/bingehack4/nethack/src/rungame.c:758
#14 0x0000562f47ffcfb4 in loadgame () at /home/loothelion/repos/bingehack4/nethack/src/rungame.c:732
#15 0x0000562f47fec92a in mainmenu () at /home/loothelion/repos/bingehack4/nethack/src/main.c:303
#16 main (argc=, argv=) at /home/loothelion/repos/bingehack4/nethack/src/main.c:367
```