[vte] lib: Fix clang build error

[Christian Persch <chpe src gnome org>]

commit 1d4eab2e8e098830aafb1001ce4b5a4100db9f4f
Author: Christian Persch <chpe src gnome org>
Date:   Sat Nov 3 22:25:48 2018 +0100

    lib: Fix clang build error
    
    Explicitly cast to integer to avoid a narrowing error.
    
    https://gitlab.gnome.org/GNOME/vte/issues/67

 src/vteseq.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/vteseq.cc b/src/vteseq.cc
index 2f2dbe0b..21b03629 100644
--- a/src/vteseq.cc
+++ b/src/vteseq.cc
@@ -1677,7 +1677,7 @@ Terminal::ACS(vte::parser::Sequence const& seq)
 
         /* Since we mostly don't implement ECMA-35 anymore, we can mostly ignore this */
 
-        switch (seq.terminator() - 0x40) {
+        switch (int(seq.terminator()) - 0x40) {
         case -10: /* '6' */
                 /* S7C1R/DECTC1 - truncate C1 controls
                  *