and Makefile.in to be consistent with changes in libpng-1.4.0rc03

in pngset.c to be consistent with other changes in version 1.2.38.

    (revising the change in 1.4.0beta99)

function.  Pass bit_depth=8 to png_build_gamma_table() when bit_depth is 16
but the PNG_16_TO_8 transform has been set, to avoid unnecessary build of
16-bit tables.

The change in version 1.2.41beta08 caused transparency to be handled wrong
in some 16-bit datastreams (Yusaku Sugai).

from contrib/pngminim/*/makefile

to disable the warnings in pngconf.h

to put png.h and pngconf.h in $prefix/include, like the other scripts,
instead of in $prefix/include/libpng.  Also revised makefile.sco
to put them in $prefix/include/libpng12 instead of in
$prefix/include/libpng/libpng12.

and added "#define PNG_NO_PEDANTIC_WARNINGS" in the libpng source files.

It will be replaced in the future with a function that accounts for gamma.

in a nonliner colorspace.

from png.h to pngpriv.h.

to accomplish alpha premultiplication when PNG_READ_COMPOSITE_NODIV_SUPPORTED
is defined.  Changed "/255" to "/255.0" in background calculations to make it
clear that the 255 is used as a double (and to prevent anyone from being
tempted to use PNG_DIVIDE_BY_255() there).

It is a pointer, not an exported function.