The default PSAPI_VERSION is controlled by WIN32_WINNT, which we set to
0x0a00 when building utils since 48a76190 (and is the default in w32api
>= 9.0.0)
In order for the built executables to run on Windows Vista, we must also
define PSAPI_VERSION as 1 (otherwise '#define GetModuleFileNameExA
K32GetModuleFileNameExA' causes a 'The procedure entry point
K32GetModuleFilenameExA could not be located in the dynamic link library
kernel32.dll' error at run time).
Also drop uneeded psapi.h from dlfcn.cc (31ddf45d), resource.cc
(34a6eeab) and ps.cc (1def2148).
Move all the source files used in utils/mingw/ into that subdirectory,
so the built objects are in the expected place.
(path.cc requires some more unpicking, and even then there is genuinely
some shared code, so use a trivial file which includes the real path.cc
so the object file is generated where expected)