[LyX/master] Fix some compiler warnings in dt2dv.c

[Juergen Spitzmueller]

commit 0c59ea386dc8719dbd3f2a5a4741eb7389adfa27
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Fri Apr 10 09:15:13 2020 +0200

    Fix some compiler warnings in dt2dv.c
---
 3rdparty/dtl/ChangeLog-LyX |    8 ++++++++
 3rdparty/dtl/dt2dv.c       |    7 ++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/3rdparty/dtl/ChangeLog-LyX b/3rdparty/dtl/ChangeLog-LyX
index c44cb35..0ef9251 100644
--- a/3rdparty/dtl/ChangeLog-LyX
+++ b/3rdparty/dtl/ChangeLog-LyX
@@ -1,6 +1,14 @@
 This file documents changes that have been done on top of the released
 version 0.6.1 from https://ctan.org/pkg/dtl
 
+Version 0.6.3 -- LyX 2.4.0
+===================================
+
+2020-04-10 Jürgen Spitzmüller <spitz at lyx.org>
+
+* dt2dv.c: Fix some compiler warnings (signedness mismatch).
+
+
 Version 0.6.2 -- 14 September 2006
 ===================================
 
diff --git a/3rdparty/dtl/dt2dv.c b/3rdparty/dtl/dt2dv.c
index 532426b..265cc84 100644
--- a/3rdparty/dtl/dt2dv.c
+++ b/3rdparty/dtl/dt2dv.c
@@ -6,13 +6,14 @@
    The author has expressed the hope that any modification will retain enough content to remain useful. He would also appreciate being acknowledged as the original author in the documentation.
    This declaration added 2008/11/14 by Clea F. Rees with the permission of Geoffrey Tobin.
 
-   - version 0.6.2 - 14 September 2006
+   - version 0.6.3 - 2020
    - Geoffrey Tobin    G.Tobin at ee.latrobe.edu.au
    - fixes:  Michal Tomczak-Jaegermann    ntomczak at vm.ucs.ualberta.ca
              Nelson H. F. Beebe    beebe at math.utah.edu
 	     Angus Leeming leeming at lyx.org: Enable dt2dv to handle .dvi files
                  containing strings longer than 1024 chars.
              Enrico Forestieri forenr at lyx.org: handle non-ASCII characters.
+             Juergen Spitzmueller spitz at lyx.org: fix compiler warnings
    - Reference:  "The DVI Driver Standard, Level 0",
                  by  The TUG DVI Driver Standards Committee.
                  Appendix A, "Device-Independent File Format".
@@ -41,7 +42,7 @@ typedef struct
 {
   COUNT num;    /* current line number */
   size_t max;   /* capacity of buf */
-  S4 wrote;     /* number of characters written into buf */
+  U4 wrote;     /* number of characters written into buf */
   size_t read;  /* position in buf of next character to read from buf */
   char * buf;   /* line buffer */
 } Line;
@@ -2206,7 +2207,7 @@ put_Lstring
 
   dvi_written += fwret;
 
-  if (fwret < lstr->l)
+  if ((long int) fwret < lstr->l)
   {
     PRINT_PROGNAME;
     fprintf (stderr,