[libpng17]Fixed conceivable but difficult to repro overflow. Also added

two test programs to generate and test a PNG which should have the problem.
[libpng17] Imported from libpng-1.7.0alpha07.tar
[libpng17] Bump version to 1.7.0alpha08
[libpng17] Corrected previous attempt at overflow detection in

png_set_unknown_chunks().
[libpng17] Imported from libpng-1.7.0alpha08.tar
[libpng17] Bump version to 1.7.0alpha09
[libpng17] Pulled changes to multi-chunk handling from libpng-1.6.0beta40.
[libpng17] Imported from libpng-1.7.0alpha09.tar
[libpng17] Bump version to 1.7.0alpha10
[libpng17] Set counter to prevent additional attempts to cache a chunk

after running out of memory or reaching a potential overflow condition.
[libpng17] Restored a "return" statement accidentally deleted from pngset.c
[libpng17] Make symbol prefixing work with the ARM neon optimizations. Also

allow pngpriv.h to be included for preprocessor definitions only, so
it can be used in non-C/C++ files.
[libpng17] Added png_get_palette_max() function.
[libpng17] Changed png_size_t to size_t throughout headers, make sRGB check

numbers consistent.
[libpng17] Fix typos in png_get_palette_max name and prototype
[libpng17] Fixed ARM support (Mans Rullgard).

Also removed stray out-of-order #endif and #ifdef
[libpng17] Ported libpng 1.5 options.awk/dfn file handling to 1.7, fixed one

bug.
[libpng16] Removed new test-driver from autogen.sh
[libpng17] Minor fixes to assembler changes, verified with a dummy .S file
[libpng17] Removed cc -E workround, corrected png_get_palette_max API. Tested

on SUN OS cc 5.9, which demonstrates the tokenization problem previously
avoided by using /lib/cpp.  Since all .dfn output is now protected
in double quotes unless it is to be macro substituted the fix should work
everywhere.