- generate_vcs_info.sh: add @CLEAN@ replacement, evaluates to just "CLEAN"
  or "UNCLEAN" depending of state of git repositor
- Generate build information into LAL...BuildInfoHeader.h instead of
  LAL...BuildInfo.c, and as #defines instead of constant variables so
  that they can be used to initialise struct fields
- Include (UN)CLEAN status and build information in LALVCSInfo struct
- Add identable LALVCSInfo struct lal...VCSIdentInfo to LAL...VCSInfo.[ch]
- Remove global variables defining VCS and build information from
  LAL...VCSInfo.[ch], since the same information is available from the
  LALVCSInfo structs lal...VCSInfo and lal...VCSIdentInfo
Original: 005ee40fcf5150df1ee94e084cd7dfe089aab021