Move configure.in to configure.ac

Rationale: configure.ac has been used as standard since approximately
2001 (source #gnu on irc.freenode.net)
Add checks for disappeared hash-defines

Two hash-defines from libpng-1.2 has disappeared, meaning cantera-lock
will not build if libpng is v1.5, maybe earlier. ./configure now checks
for these hash-defines and defines them if not found.
Add config.h and fix pathmistake
Properly check for hash define.
Remove the circle and play with colors.