This presents value semantics for a stack of constant values.
Internally it shares ownership to avoid copies. Previously
this was implemented by `cmListFileBacktrace` explicitly,
but the approach can be re-used for other kinds of stacks.
In a per-component installation the generated installation scripts
are invoked once for each component.
Per default custom installation script code added by install(CODE|SCRIPT)
only runs for one specific component in this context.
The new ALL_COMPONENTS option allows custom script code to be run once
for each component being installed.
This is preparation for an upcoming merge request, which will add
a new cmInstallGenerator that returns false if there are errors in
the Compute() step.
Suppress some cases in `Source/cmGeneratorExpressionNode.cxx` and
`Source/cmUVHandlePtr.h` where a few older compilers require a
user-defined default constructor (with `{}`).
Before this change, install rules created by add_subdirectory()
would be executed after all of the top-level install rules, even
if they were declared before the top-level rules. This change
adds a new policy, CMP0082, which interleaves the add_subdirectory()
install rules with the other install rules so they are run in the
correct order.
