Cleanup uses of sprintf so we can deprecate it.

Also cleans up two instances of open() with useless mode params, and
changes a few uses of snprintf to use sizeof(buffer) instead of
hardcoded buffer sizes.

Change-Id: If11591003d910c995e72ad8f75afd072c255a3c5
diff --git a/init/parser.cpp b/init/parser.cpp
index 8193729..ae103ec 100644
--- a/init/parser.cpp
+++ b/init/parser.cpp
@@ -12,7 +12,7 @@
     char buf[128];
     int off;
 
-    snprintf(buf, 128, "%s: %d: ", state->filename, state->line);
+    snprintf(buf, sizeof(buf), "%s: %d: ", state->filename, state->line);
     buf[127] = 0;
     off = strlen(buf);