Add commithash of the kxml_compiler to the generated file's comment section

[martonmiklos]

Sometimes it would be great to know from a generated parser/generator, that which version of the kxml_compiler generated it, so it would be useful to generate this to the heading comments.

On bash based envs we could borrow the getrevision.sh from the flashrom for this purpose: https://github.com/flashrom/flashrom/blob/master/util/getrevision.sh

On Windows we would need to came up with a batchfile.

[winterheart]

Hi. This can be achieved with Git module and add_custom_command in CMake. In QMake it would be

GIT_VERSION = $$system(git --git-dir $$PWD/.git --work-tree $$PWD describe --always --tags)

but I prefer dynamic file version.h generation.