Nitpicks to the previous commit.

We enforce by assertion that the target buffer size is nonzero before
subtracting 1 from it; the call to fatal() is replaced by another
assert so that it will give clearer diagnostic information if it
fails; the variable holding the return value of strlen should be
size_t and its declaration should be in a C90-compatible location.
Finally, the reason why the function needs to be exist is clarified.

misc.c

@@ -361,15 +361,14 @@ void draw_text_outline(drawing *dr, int x, int y, int fonttype,
 
 }
 
-/* kludge for non-compliant sprintf() */
+/* kludge for sprintf() in Rockbox not supporting "%-8.8s" */
 void copy_left_justified(char *buf, size_t sz, const char *str)
 {
+    size_t len = strlen(str);
+    assert(sz > 0);
     memset(buf, ' ', sz - 1);
-    int len = strlen(str);
-    if(len <= sz - 1)
+    assert(len <= sz - 1);
     memcpy(buf, str, len);
-    else
-        fatal("overrun");
     buf[sz - 1] = 0;
 }