cmake: Fix ABI version for shared library and improve MSVC output artifacts naming

[hebasto]

1. Fixed ABI version for a shared library.

To test, one needs to simulate a release with backward-compatible API changes, which means:

• increment of LIB_VERSION_CURRENT
• setting LIB_VERSION_REVISION to zero
• increment of LIB_VERSION_AGE

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2. When using Visual Studio generator, the "lib" prefix is not added automatically.

Also added ABI-version suffix for a shared library (not bothering about a static library, as it already has the "_static" suffix to avoid name collision with DLL import library; should be revisited after #1230).

On master (5658209):

• shared library: secp256k1.dll and secp256k1.lib
• static library: secp256k1_static.lib

With this PR:

• shared library: libsecp256k1-2.dll and libsecp256k1-2.lib
• static library: libsecp256k1_static.lib

[real-or-random]

Concept ACK, also based on the fact that autotools+mingw adds the lib prefix:

With ./configure --enable-shared --enable-static --enable-dev-mode --host=x86_64-w64-mingw32, I get this in .libs:

-rwxr-xr-x 1 1740850 Mar 11 14:58 bench_ecmult.exe*
-rw-r--r-- 1    5990 Mar 11 14:58 bench_ecmult_ltshwrapper
-rwxr-xr-x 1  183064 Mar 11 14:58 bench.exe*
-rwxr-xr-x 1 1728983 Mar 11 14:58 bench_internal.exe*
-rw-r--r-- 1    6010 Mar 11 14:58 bench_internal_ltshwrapper
-rw-r--r-- 1    6360 Mar 11 14:58 bench_ltshwrapper
-rwxr-xr-x 1 1622008 Mar 11 14:58 libsecp256k1-2.dll*
-rw-r--r-- 1 1620676 Mar 11 14:58 libsecp256k1.a
-rw-r--r-- 1   50552 Mar 11 14:58 libsecp256k1.dll.a
lrwxrwxrwx 1      18 Mar 11 14:58 libsecp256k1.la -> ../libsecp256k1.la
-rw-r--r-- 1     936 Mar 11 14:58 libsecp256k1.lai
-rw-r--r-- 1 1120192 Mar 11 14:58 libsecp256k1_precomputed.a
lrwxrwxrwx 1      30 Mar 11 14:58 libsecp256k1_precomputed.la -> ../libsecp256k1_precomputed.la
-rw-r--r-- 1   32675 Mar 11 14:58 lt-bench.c
-rw-r--r-- 1   32021 Mar 11 14:58 lt-bench_ecmult.c
-rw-r--r-- 1   32049 Mar 11 14:58 lt-bench_internal.c

Do we also want the -2 ABI version suffix?

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By the way, autotools+MSVC doesn't add the prefix... But that's a somewhat strange combination that probably noone uses, except our CI.
With ./configure --enable-shared --enable-static --enable-dev-mode --host=x86_64-w64-mingw32 CC=/opt/msvc/bin/x64/cl CFLAGS="-nologo -diagnostics:caret" LDFLAGS="-XCClinker -nologo -XCClinker -diagnostics:caret" NM="/opt/msvc/bin/x64/dumpbin -symbols -headers" AR="/opt/msvc/bin/x64/lib", I get this in .libs:

-rwxr-xr-x 1 1330176 Mar 11 15:05 bench_ecmult.exe*
-rw-r--r-- 1    5990 Mar 11 15:05 bench_ecmult_ltshwrapper
-rwxr-xr-x 1  157184 Mar 11 15:05 bench.exe*
-rwxr-xr-x 1 1320960 Mar 11 15:05 bench_internal.exe*
-rw-r--r-- 1    6010 Mar 11 15:05 bench_internal_ltshwrapper
-rw-r--r-- 1    6360 Mar 11 15:05 bench_ltshwrapper
lrwxrwxrwx 1      18 Mar 11 15:05 libsecp256k1.la -> ../libsecp256k1.la
-rw-r--r-- 1     928 Mar 11 15:05 libsecp256k1.lai
lrwxrwxrwx 1      30 Mar 11 15:05 libsecp256k1_precomputed.la -> ../libsecp256k1_precomputed.la
-rw-r--r-- 1   32675 Mar 11 15:05 lt-bench.c
-rw-r--r-- 1   32021 Mar 11 15:05 lt-bench_ecmult.c
-rw-r--r-- 1   32049 Mar 11 15:05 lt-bench_internal.c
-rw-r--r-- 1 1333760 Mar 11 15:05 secp256k1-2.dll
-rw-r--r-- 1    3180 Mar 11 15:05 secp256k1-2.dll.exp
-rw-r--r-- 1   12123 Mar 11 15:05 secp256k1.dll.exp
-rw-r--r-- 1   20200 Mar 11 15:05 secp256k1.dll.lib
-rw-r--r-- 1    2214 Mar 11 15:05 secp256k1.exp
-rw-r--r-- 1 1363666 Mar 11 15:05 secp256k1.lib
-rw-r--r-- 1 1123338 Mar 11 15:05 secp256k1_precomputed.lib

[hebasto]

Do we also want the -2 ABI version suffix?

Incidentally, I'm thinking about the same at this moment :)

[hebasto]

Updated ff0a509 -> e2e0f47 (pr1237.01 -> pr1237.02, diff):

• addressed @real-or-random's comment:

Do we also want the -2 ABI version suffix?

[sipa]

Concept ACK

[hebasto]

Also I've noticed and fixed a wrong ABI version for a shared library.

The PR description has been updated as well.

[hebasto]

Also I've noticed and fixed a wrong ABI version for a shared library.

The ABI version fix has been moved into a separated #1270.

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Drafted for now.

[hebasto]

Closing in favour of #1270.