Added -private flag for entry points that shouldn't be imported from
other dlls.
Support PRIVATE flag in .def files (based on a patch by Jon
Griffiths).

diff --git a/tools/winebuild/parser.c b/tools/winebuild/parser.c
index 0b6118b..8cca02e 100644
--- a/tools/winebuild/parser.c
+++ b/tools/winebuild/parser.c
@@ -62,6 +62,7 @@
     "i386",        /* FLAG_I386 */
     "register",    /* FLAG_REGISTER */
     "interrupt",   /* FLAG_INTERRUPT */
+    "private",     /* FLAG_PRIVATE */
     NULL
 };