libLAS 1.2 requires GDAL 1.7 (unreleased)

[hobu]

The GDAL code that libLAS uses depends on some unreleased stuff. We should either accommodate GDAL <= 1.7.

 ../src/.libs/liblas.so: undefined reference to
 `SetGeogCSCitation(gtiff*, OGRSpatialReference*, char*, int, short)'
 ../src/.libs/liblas.so: undefined reference to
 `SetCitationToSRS(gtiff*, char*, int, geokey_t, OGRSpatialReference*,
 int*)'
 ../src/.libs/liblas.so: undefined reference to
 `SetLinearUnitCitation(gtiff*, char*)'
 ../src/.libs/liblas.so: undefined reference to
 `GetGeogCSFromCitation(char*, int, geokey_t, char**, char**, char**, char**, char**)'

[hobu]

Fixed in trunk in r1316 and in the 1.2 branch in r1315. The problem is gt_citation.cpp from GDAL was not included, which gt_wkt_srs.cpp uses.