mdp: Add patch for unsigned chars

packages/mdp/src-viewer.c.patch

@@ -0,0 +1,14 @@
+Submitted upstream at https://github.com/visit1985/mdp/pull/128
+
+diff -u -r ../mdp-1.0.12/src/viewer.c ./src/viewer.c
+--- ../mdp-1.0.12/src/viewer.c	2018-01-14 13:30:39.000000000 +0000
++++ ./src/viewer.c	2018-06-07 23:03:32.846968101 +0000
+@@ -982,7 +982,7 @@
+ 
+ int get_slide_number(char init) {
+     int retval = init - '0';
+-    char c;
++    int c;
+     // block for tenths of a second when using getch, ERR if no input
+     halfdelay(GOTO_SLIDE_DELAY);
+     while((c = getch()) != ERR) {