Fix the way FT headers are included

FreeType headers have to be included with macros defined in ftheaders.h.
Not doing so breaks when the FreeType header location changes as was the
case between FreeType 2.6.0 and 2.6.2.

Patch by jshin@chromium.org
BUG=pdfium:362
R=jshin@chromium.org, tsepez@chromium.org

Review URL: https://codereview.chromium.org/1587333002 .
diff --git a/core/include/fxge/fx_freetype.h b/core/include/fxge/fx_freetype.h
index c7c8295..5721784 100644
--- a/core/include/fxge/fx_freetype.h
+++ b/core/include/fxge/fx_freetype.h
@@ -8,12 +8,13 @@
 #define CORE_INCLUDE_FXGE_FX_FREETYPE_H_
 
 #include <ft2build.h>
-#include <freetype.h>
-#include <ftglyph.h>
-#include <ftlcdfil.h>
-#include <ftmm.h>
-#include <ftoutln.h>
-#include <tttables.h>
+#include FT_FREETYPE_H
+#include FT_GLYPH_H
+#include FT_LCD_FILTER_H
+#include FT_MULTIPLE_MASTERS_H
+#include FT_OUTLINE_H
+#include FT_TRUETYPE_TABLES_H
+
 #ifdef __cplusplus
 extern "C" {
 #endif