Fix 64-bit type problems in dumper.exe
* dumper.cc: Througout, cast pid to unsigned int, change addresses
and sizes from DWORD to SIZE_T, and use %p for pointer addresses.
(dumper::add_mem_region): Change size type to SIZE_T.
(dumper::split_add_mem_region): Ditto.
* dumper.h (struct process_mem_region): Change size type to SIZE_T.
(class exclusion): Change last, size, and step types to size_t.
(exclusion::exclusion): Change argument type to size_t.
(exclusion::add): Change mem_size type to SIZE_T.
(dumper::add_mem_region): Change size type to SIZE_T.
(dumper::split_add_mem_region): Ditto.
(psapi_get_module_name): Change BaseAddress type to LPVOID.
* module_info.cc (psapi_get_module_name): Ditto.
* parse_pe.cc: Througout, change addresses and sizes from DWORD to
SIZE_T, and use %p for pointer addresses.
(exclusion::add): Change mem_size type to SIZE_T.
	* cygwin.sc.in (.gnu_debuglink_overlay): Drop "64" in dbg file name.
* Makefile.in (libcygwin.a): Move --target flag from here...
(toolopts): to here, to be used by both mkimport and speclib.
* speclib: Omit leading underscore in symbol names on x86_64.