Local cfg/CONFIG* files missed when Base set INSTALL_LOCATION

Bug reported by Joao Paulo Martins (I think).

When building a support module against a Base that was built with INSTALL_LOCATION set, any cfg/CONFIG* files provided by the support module do not get included by its own build unless it also has INSTALL_LOCATION set to either the same as Base (or possibly the same as some other dependent support module that also appears in its RELEASE file).

A workaround is to remove the setting of INSTALL_LOCATION from the configure/CONFIG_SITE file (or wherever it does get set) in the installed copy of Base.

This probably affects all versions of Base, and happens because TOP_CFG_CONFIGS are included by the Base/configure/CONFIG file, and support modules have to override INSTALL_LOCATION after that file has been included because the Base setting gets pulled in during CONFIG.