If I ask for version 2, the current trunk version (version 3), will say it is compatible, which is erroneous.

Do not consider different major versions compatible in cmake config file

Reverts "Set the default value of exposure_weight in createMergeMertens to 1.0" because it breaks source code compatibility and tests
This reverts commit dbfd6a3d.

MergeDebevec takes camera response function as an optional input
parameter. Despite being clearly marked as input, this matrix is
overwritten during processing.

This commit adds a temporary matrix to store the log response and avoid
modification of the input.