Make it proper C
regtest: Update references also for tests that no longer crash

We are currently updating the refs only when we have checksums to
compare, but if a test used to crash there's no md5 file in refs.
write correct size in trailer dict

Bug #86063
Use Default colorspaces if present instead of Device colorspaces

Fixes part of #68986
Solve blend mode problem in CYMK and DeviceN for separable blend modes

Fixes part of #68986
Use correct LAB byte array for lcms input

Bug #86388
cofigure: print "no" instead of "auto" if lcms not found
The isfinite macro is defined on SunOS under c99

Bug #86869
warning: "_FILE_OFFSET_BITS" redefined

Bug #86870
Run dos2unix as suggested by Volker Grabsch
0.29.0