Lift `FT_Int64` type to global (internal) FreeType use.

* src/base/ftcalc.c (FT_Int64) [!FT_INT64]: Move declaration to...
* include/freetype/config/integer-types.h: ... this file.
  (FT_UInt64) [!FT_INT64]: New structure.
  (FT_INT64_ZERO): New macro.
2 files changed