dd vhea/vmtx table support.

- Added vhea.{cc,h} and vmtx.{cc,h}.
- Added metrics.{cc,h} to integrate common functions of hhea/hmtx and vhea/vmtx.
- Moved functions in hhea.cc to metrics.cc.

BUG=77386
TEST=http://code.google.com/p/ots/wiki/HowToTestOts (verified with 3500+ font files)
TEST=test/table_dependencies_test.cc


git-svn-id: http://ots.googlecode.com/svn/trunk@61 a4e77c2c-9104-11de-800e-5b313e0d2bf3
diff --git a/src/hhea.h b/src/hhea.h
index 99aafde..bdea9aa 100644
--- a/src/hhea.h
+++ b/src/hhea.h
@@ -5,22 +5,13 @@
 #ifndef OTS_HHEA_H_
 #define OTS_HHEA_H_
 
+#include "metrics.h"
 #include "ots.h"
 
 namespace ots {
 
 struct OpenTypeHHEA {
-  int16_t ascent;
-  int16_t descent;
-  int16_t linegap;
-  uint16_t adv_width_max;
-  int16_t min_lsb;
-  int16_t min_rsb;
-  int16_t x_max_extent;
-  int16_t caret_slope_rise;
-  int16_t caret_slope_run;
-  int16_t caret_offset;
-  uint16_t num_hmetrics;
+  OpenTypeMetricsHeader header;
 };
 
 }  // namespace ots