Link with .def files

MSVC's `link.exe` automatically finds `__cdecl` C functions (which are
decorated with a leading underscore by the compiler) when they are
mentioned in a `.def` f

Link with .def files

MSVC's `link.exe` automatically finds `__cdecl` C functions (which are
decorated with a leading underscore by the compiler) when they are
mentioned in a `.def` file without the leading underscore. This is an
[under-documented feature][1] of MSVC's `link.exe`. C++Builder's
`ilink32.exe` doesn't do this, and thus needs the name-translation in
the `.def` file. Then `implib.exe` needs to be told to re-add it.

(The Clang-based `bcc32c.exe` doesn't implement the [`-vu` or `-u-`][2]
options to skip adding the leading underscore to `__cdecl` C function
names, so this is the only way to have things work with non-underscored
export names in the DLLs.)

[1]: https://github.com/MicrosoftDocs/cpp-docs/issues/2653
[2]: http://docwiki.embarcadero.com/RADStudio/Sydney/en/Options_Not_Supported_by_Clang-enhanced_C%2B%2B_Compilers#BCC32_Options_that_Are_Not_Supported_by_Clang-enhanced_C.2B.2B_Compilers

Also silence linker warnings on duplicate symbols and ensure that error-
case cleanup in link rules work in C++Builder's `make.exe`.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/13540)

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