and fix some other small typos.

minor change from the previous (unreleased) ABI/API to hide the exact value
used for Macs - it's not a good idea to embed this in the ABI!

argument names file_gamma, int_file_gamma, and srgb_intent consistently.

Also removed two obsolete comments from png.c

that CCP writes to standard output by default (Martin Banky).

Studio 2010 (John Bowler).

and shortening problems on assignment but also a few difficult to optimize
(for GCC) loops (John Bowler).

literal pointers declare them (John Bowler).
Many APIs did not change their arguments but were not declared using
PNG_CONST.  This change corrects this.  In a few cases APIs that return
constant string literal pointers have also been changed to declare this.
Unlike the argument change this may require app changes; however the
results could never be written to (the app would crash on some platforms
where strings are not writable), so this seems advisable.

that were recently introduced, mostly resulting from
safe but uncast assignments to shorter integers.  Also added a zlib
VStudio release library project because the latest zlib Official Windows
build does not include such a thing.

  Fixed point APIs are now supported throughout (no missing APIs).
  Internal fixed point arithmetic support exists for all internal floating
    point operations.
  sCAL validates the floating point strings it is passed.
  Safe, albeit rudimentary, Watcom support is provided by PNG_API_RULE==2
  Two new APIs exist to get the number of passes without turning on the
    PNG_INTERLACE transform and to get the number of rows in the current
    pass.
  A new test program, pngvalid.c, validates the gamma code.
  Errors in the 16 bit gamma correction (overflows) have been corrected.
  cHRM chunk testing is done consistently (previously the floating point
    API bypassed it, because the test really didn't work on FP, now the test
    is performed on the actual values to be stored in the PNG file so it
    works in the FP case too.)
  Most floating point APIs now simply call the fixed point APIs after
    converting the values to the fixed point form used in the PNG file.
  The standard headers no longer include zlib.h, which is currently only
    required for pngstruct.h and can therefore be internal.
  (Patches by John Bowler)

    floating point APIs, but not both.

and disable.  Corrected scripts/options.awk to handle both command line
options and options specified in the .dfa files.