Add buffer flags

New API:

	hb_buffer_flags_t

	HB_BUFFER_FLAGS_DEFAULT
	HB_BUFFER_FLAG_BOT
	HB_BUFFER_FLAG_EOT
	HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES

	hb_buffer_set_flags()
	hb_buffer_get_flags()

We use the BOT flag to decide whether to insert dottedcircle if the
first char in the buffer is a combining mark.

The PRESERVE_DEFAULT_IGNORABLES flag prevents removal of characters like
ZWNJ/ZWJ/...

src/hb-buffer.h

diff --git a/src/hb-buffer.h b/src/hb-buffer.h
index fbd809c..533bac8 100644
--- a/src/hb-buffer.h
+++ b/src/hb-buffer.h
@@ -68,6 +68,12 @@
   HB_BUFFER_CONTENT_TYPE_GLYPHS
 } hb_buffer_content_type_t;
 
+typedef enum {
+  HB_BUFFER_FLAGS_DEFAULT			= 0x00000000,
+  HB_BUFFER_FLAG_BOT				= 0x00000001, /* Beginning-of-text */
+  HB_BUFFER_FLAG_EOT				= 0x00000002, /* End-of-text */
+  HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES	= 0x00000004
+} hb_buffer_flags_t;
 
 hb_buffer_t *
 hb_buffer_create (void);
@@ -129,6 +135,13 @@
 hb_language_t
 hb_buffer_get_language (hb_buffer_t *buffer);
 
+void
+hb_buffer_set_flags (hb_buffer_t       *buffer,
+		     hb_buffer_flags_t  flags);
+
+hb_buffer_flags_t
+hb_buffer_get_flags (hb_buffer_t *buffer);
+
 
 /* Resets the buffer.  Afterwards it's as if it was just created,
  * except that it has a larger buffer allocated perhaps... */