Log Message:
Update to 1.2.22:

version 1.2.21beta1 [September 14, 2007]
  Fixed various mistakes reported by George Cook and Jeff Phillips:
  logical vs bitwise NOT in pngrtran.c, bug introduced in 1.2.19rc2
  16-bit cheap transparency expansion, bug introduced in 1.2.19beta2
  errors with sizeof(unknown_chunk.name), bugs introduced in 1.2.19beta11
  <= compare with unsigned var in pngset.c, should be ==.

version 1.2.21beta2 [September 18, 2007]
  Removed some extraneous typecasts.

version 1.2.21rc1 [September 25, 2007]
  Fixed potential out-of-bounds reads in png_handle_pCAL() and
    png_handle_ztXt() ("flayer" results reported by Tavis Ormandy).

version 1.2.21rc2 [September 26, 2007]
  Fixed potential out-of-bounds reads in png_handle_sCAL(),
    png_handle_iTXt(), and png_push_read_tEXt().
  Remove some PNG_CONST declarations from pngwutil.c to avoid compiler warnings
  Revised makefiles to update paths in libpng.pc properly.

version 1.2.21rc3 [September 27, 2007]
  Revised makefiles to update "Libs" in libpng.pc properly.

version 1.0.29 and 1.2.21 [October 4, 2007]
  No changes.

version 1.2.22beta1 [October 4, 2007]
  Again, fixed logical vs bitwise NOT in pngrtran.c, bug introduced
    in 1.2.19rc2

version 1.2.22beta2 [October 5, 2007]
  Fixed string length error in pngset.c (caused crashes while decoding iCCP)
  Add terminating NULL after each instance of png_strncpy().

version 1.2.22beta3 [October 6, 2007]
  Fix two off-by-one terminating NULL after png_strncpy().

version 1.2.22beta4 [October 7, 2007]
  Changed some 0 to '\0'.

version 1.0.30rc1 and 1.2.22rc1 [October 8, 2007]
  No changes.

version 1.0.30 and 1.2.22 [October 13, 2007]
  No changes.