handling. Internal changes only except for a new option to avoid compiling
in the png_build_grayscale_palette API (which is not used at all internally.)
The main change is to move the transform tests (READ_TRANSFORMS,
WRITE_TRANSFORMS) up one level to the caller of the APIs.

table, to avoid cpp failure on SunOS (introduced PNG_BUILDING_SYMBOL_TABLE
macro).

This reverts commit 2438825d.

accommodate the old VisualC++ preprocessor.
Defined PNG_ALLOCATED to empty for MSC_VER < 1300.

argument names file_gamma, int_file_gamma, and srgb_intent consistently.