Remove the Name variable, which duplicates an attribute.
Replace hardcoded Mains with Name.
Remove transitional Library_Type variable from library projects.
Make explicit that Library_Version is only useful during relocatable
builds.
Compute Library_Version from Library_Name, in case it ever differs
from Name.
Make the list of possible Library_Type values explicit (the
documentation mentions "dynamic").
To avoid conflict with installed gnatcoll.gpr where GNATCOLL_BUILD means
library type.
Part of S709-037.
Change-Id: I372b3fc7b35faf14a223465069968ff1e5550250
To have a unified external for all GNATCOLL project, as discussed for
gnatcoll-db.
Part of S709-037.
Change-Id: I5b6c843df6926288b8906a8c285a6d682394d7bf
Like for gnatcoll_core, these externals allow gnatcoll_*.gpr to be used
from a project that defines the BUILD external in an incompatible way.
Part of S709-037.
Change-Id: Ib69453688c4c3ea112aa8b00d3a610bdc2f5426f
