[DO NOT MERGE] Fix the way FreeType headers are incldued.

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.

This issue blocks updating FreeType to 2.6.2.

Fixed in the upstream: 
 https://pdfium.googlesource.com/pdfium/+/56461d66054c53fe3abc88208eaf5d84e80e6551

This CL is back-porting the following AOSP master CL:
  https://android-review.googlesource.com/#/c/196608/

BUG: 24296662

Change-Id: I174a6ad2d3efcce5a68317957869ae898869f850
Signed-off-by: Jungshik Shin <jungshik@google.com>
diff --git a/core/include/fxge/fx_freetype.h b/core/include/fxge/fx_freetype.h
index 6975ead..7ad9812 100644
--- a/core/include/fxge/fx_freetype.h
+++ b/core/include/fxge/fx_freetype.h
@@ -8,12 +8,12 @@
 #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