re PR c++/19555 (specialized in the wrong namespace causes an ICE)
PR c++/19555
* cp-tree.h (DECL_USE_TEMPLATE): Expand documentation.
* decl.c (duplicate_decls): Do not discard
DECL_IMPLICIT_INSTANTIATION when merging declarations.
(start_decl): Do not SET_DECL_TEMPLATE_SPECIALIZATION for
variables that do not have DECL_USE_TEMPLATE.
PR c++/19555
* g++.dg/template/static10.C: New test.