### Reduce symbol and macro pollution from epicsAtomic.h on WIN32

`epicsAtomic.h` no longer pulls in as many unneeded declarations and macros from
`windows.h`. Prior to this change, including `epicsAtomic.h` at the wrong time
could result in unexpected compiler errors. Due to the nature of `windows.h`,
some unneeded declarations are still pulled in, however the number is greatly reduced.
Code that needs these declarations should explicitly include `windows.h` before `epicsAtomic.h`.