Fix compatibility with GCC 4.x.

Fix compatibility with GCC 4.x.
* Makefile.am (setup_LDFLAGS): Pass -static to compiler instead of
linker so that libgcc is statically linked as well.
(autoload.o): Disable optimization.
* localdir.cc (browse_cb): Fix "jump to case label crosses
initialization" error.
* mklink2.cc (sfli): Fix "non-local variable uses anonymous type"
warning.
* ntdll.h: Fix "redeclared without dllimport attribute: previous
dllimport ignored" warnings.
* package_message.h (display): Fix "'exit' was not declared in this
scope" error.