curses_putmixed() initial attempt

The curses interface was using genl_putmixed() which doesn't
preserve the symbol actually used for a glyph on the display.
This is a first-attempt at implementing curses_putmixed().

On Linux you'll need to distribute the Makefiles again
    sh sys/unix/setup.sh sys/unix/hints/linux.370

On macOS, you'll need to distribute the Makefiles again
    sh sys/unix/setup.sh sys/unix/hints/macOS.370

src/utf8map.c

@@ -542,6 +542,33 @@ mixed_to_utf8(char *buf, size_t bufsz, const char *str, int *retflags)
     return buf;
 }
 
+/*
+ * helper routine if a window port wants to extract the unicode
+ * representation from a glyph representation in the string;
+ * the returned string is the remainder of the string after
+ * extracting the \GNNNNNNNN information.
+ */
+const char *
+mixed_to_glyphinfo(const char *str, glyph_info *gip)
+{
+    int dcount, ggv;
+
+    if (!str || !gip)
+        return " ";
+
+    *gip = nul_glyphinfo;
+    if (*str == '\\' && *(str + 1) == 'G') {
+        if ((dcount = decode_glyph(str + 2, &ggv))) {
+            map_glyphinfo(0, 0, ggv, 0, gip);
+            /* 'str' is ready for the next loop iteration and
+                '*str' should not be copied at the end of this
+                iteration */
+            str += (dcount + 2);
+        }
+    }
+    return str;
+}
+
 void
 dump_all_glyphids(FILE *fp)
 {