Update to libpng 1.2.50, add parameter to batch files to accept a build target (like "build-windows.bat png")

This update may not have been necessary (investigating interlaced PNG support) but may as well commit it now that its done
Added missing tar
Updated Mac and iOS binaries
freetype-2.5.0.1

Adobe and Google contribute to new CFF engine. Which is now default for fonts rendering. I think it makes a good reason to change from the 2.4.x to the 2.5.x series. 

Changes:
CHANGES BETWEEN 2.4.12 and 2.5

  I. IMPORTANT BUG FIXES

    - The cache manager function `FTC_Manager_Reset'  didn't flush the
      cache.


  II. IMPORTANT CHANGES

    - Behdad Esfahbod  (on behalf  of Google) contributed  support for
      color embedded bitmaps (eg. color emoji).

      A  new  load  flag,  FT_LOAD_COLOR, makes  FreeType  load  color
      embedded-bitmaps, following this draft specification

        https://color-emoji.googlecode.com/git/specification/v1.html

      which defines two new SFNT  tables, `CBDT' and `CBLC' (named and
      modeled  after  `EBDT'  and `EBLC',  respectively).   The  color
      bitmaps  are  stored in  the  new  FT_PIXEL_MODE_BGRA format  to
      represent BGRA  pre-multiplied sRGB  images.  If PNG  support is
      available,  PNG color  images as  defined in  the same  proposed
      specification are supported also.

      Note that  color bitmaps  are converted  to grayscale  if client
      didn't ask for color.

    - As  announced in  the  previous release,  the  old FreeType  CFF
      engine  is now  disabled by  default.  It  can be  conditionally
      compiled     by     defining     the     configuration     macro
      CFF_CONFIG_OPTION_OLD_ENGINE.

    - As announced in the previous release,  all code related to macro
      FT_CONFIG_OPTION_OLD_INTERNALS  has been removed,  thus becoming
      obsolete.


  III. MISCELLANEOUS

    - The  property API  (`FT_Property_Get' and  `FT_Property_Set') is
      now declared as stable.

      The  exception,   however,  are  the   experimental  auto-hinter
      properties `glyph-to-script-map' and `fallback-script' which are
      subject to change in a forthcoming release.

    - `ftview' has been updated to  support color embedded bitmaps; it
      can be toggled on and off  with key `c'.  The small cache toggle
      is now key `K'.

    - It  is now  possible  to  control the  version  of the  TrueType
      hinting engine  using the new `interpreter-version'  property of
      the  `truetype' module:  Versions 35  and 38  (the default)  are
      supported,  which  roughly  corresponds to  disable  and  enable
      subpixel hinting support, respectively.

      In  both  `ftview'  and  `ftdiff',  switching  between  the  two
      versions  can be  done  with  key `H'.   In  the `ftbench'  demo
      program, command line option `-H'  has been extended to activate
      the non-default interpreter version.

    - The `ttdebug' program has been further improved.  In particular,
      it accepts a new command line  option `-H' to select the hinting
      engine.

    - Another round of TrueType subpixel hinting fixes.

    - The `apinames' tool can now create an import file for NetWare.

    - 64bit compilation of the new CFF engine was buggy.

    - Some fixes to improve robustness in memory-tight situations.
Merge branch 'patch-1'
Merge with master ...