[2019-12-05] - Found with Honggfuzz - CVE-2019-19601

Buffer overflow in the TexOpen() function, in detex.l.

Issue can be reproduced by running:

```
detex test01
```

```
=================================================================
==2795==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000db1540 at pc 0x00000043a607 bp 0x7ffdb2beab20 sp 0x7ffdb2bea2b8
WRITE of size 6062 at 0x000000db1540 thread T0
    #0 0x43a606 in vsprintf (/home/fcambus/opendetex-2.8.5/detex+0x43a606)
    #1 0x43b593 in sprintf (/home/fcambus/opendetex-2.8.5/detex+0x43b593)
    #2 0x4cbbb5 in TexOpen /home/fcambus/opendetex-2.8.5/detex.l:904:9
    #3 0x4c6cbd in IncludeFile /home/fcambus/opendetex-2.8.5/detex.l:756:14
    #4 0x4c4382 in yylex /home/fcambus/opendetex-2.8.5/detex.l
    #5 0x4cb20e in main /home/fcambus/opendetex-2.8.5/detex.l:602:12
    #6 0x7fd1c14491e2 in __libc_start_main /build/glibc-4WA41p/glibc-2.30/csu/../csu/libc-start.c:308:16
    #7 0x41b34d in _start (/home/fcambus/opendetex-2.8.5/detex+0x41b34d)

0x000000db1540 is located 0 bytes to the right of global variable 'sbFullPath' defined in 'detex.l:893:14' (0xdb0540) of size 4096
SUMMARY: AddressSanitizer: global-buffer-overflow (/home/fcambus/opendetex-2.8.5/detex+0x43a606) in vsprintf
Shadow bytes around the buggy address:
  0x0000801ae250: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801ae260: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801ae270: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801ae280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801ae290: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0000801ae2a0: 00 00 00 00 00 00 00 00[f9]f9 f9 f9 f9 f9 f9 f9
  0x0000801ae2b0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0000801ae2c0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0000801ae2d0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0000801ae2e0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0000801ae2f0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==2795==ABORTING
```