cpprest_compat breaks cURL header when building with Clang 14

[lilianmoraru]

#define dllimport inside cpprest_compat.h breaks curl.h on Clang 14.

See minimized example here: godbolt

The issue was initially reported to LLVM.
The LLVM issue was closed. For the reason, see these comments: comment1 and comment2.

[barcharcraz]

Yeah I can see why they closed that one. This header is pretty horrible.

[laveur]

FYI this project is now dead. You should move away from cpprest ASAP. See the readme file.

[barcharcraz]

Indeed, we will fix any super critical bugs, but we highly, highly, highly recommend folks move to another library. We usually recommend libcurl.