[glabels] Fix portability issue due to signedness of char.

[Jim Evins <jimevins src gnome org>]

commit 258d95c416fa583eda5265a655d8f8e9ba87e546
Author: Jim Evins <evins snaught com>
Date:   Sat Mar 31 09:18:09 2018 -0400

    Fix portability issue due to signedness of char.

 src/merge-text.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/merge-text.c b/src/merge-text.c
index f24ae01..06e45ec 100644
--- a/src/merge-text.c
+++ b/src/merge-text.c
@@ -421,7 +421,7 @@ gl_read_encoding(FILE* fp) {
  * g_iconv is used to convert input characters to GDK-standard UTF8 format.
  */
 
-static gchar
+static gint
 gl_getc(glMergeText *merge_text) {
         if (merge_text->priv->buf_pos < merge_text->priv->buf_len) {
                 return merge_text->priv->char_buf[merge_text->priv->buf_pos++];