Support for <project> placeholder for patterns

[garonne <garonne@…>]

CMT provides several placeholders for use within patterns, most specifically <package>, which is replaced by the package name at build time. I'd like to see <project> added in the same way. One motivation for this is shown by the existing installed_library pattern. This essentially has:

    macro_append <package>_linkopts " -L$(bin) -l<package> <extras> "

which is anyway incorrect (so needs to be fixed). The correct fix would be something like:

    macro_append <package>_linkopts "" \
                 <project>_without_installarea " -L$(<PACKAGE>ROOT)/$ 
(<package>_tag)" ; \
    macro_append <package>_linkopts            " -l<package> <extras> "

Which would use the library from within the package if no InstallArea is present, and otherwise use the symlinked version from the InstallArea.

[garonne]

The <project> placeholder already exists since v1r18p200606.