This PR moves the public API headers into a top-level include directory. This makes it easier to find the public API of cvc5 and makes the install headers script obsolete.
Fixes#9553Fixes#9556
The public cvc5 API now lives in the cvc5 namespace. All internal parts were moved into the (new) internal namespace.
The final hierarchy will be as follows:
cvc5
~~ public API
::context
::internal
::parser
::main
After this PR it will be:
cvc5
~~ public API
::internal
::context
::main
::parser
