- add macro PACKAGE_VERSION_REVISION dealt with in bootstrap.ci
- restrict to those macros only that are mangled by bootstrap.ci
- update comments on the file's purpose and the processes around it
Following http://sourceforge.net/p/opensc/mailman/message/32009859/
* 'configure.ac' is not mored created by bootstrap script, but present in source
* 'version.m4' is introduced and contains the 'volatile' package settings:
settings that can be changed for the needs of particular build (ex. change PACKAGE_SUFFIX using the Git 'describe' or 'commit' data)
* 'bootstrap' script facilitate change of the package setting during the 'autoconf' phase