Fix Windows alt/control key modifiers

[Yaraslaut]

Closes #1408

Also, fixes my locall build with libssh support, see target names: libssh2/libssh2#1104

[christianparpart]

Thank you, @Yaraslaut

[christianparpart]

CMake Error at src/vtpty/CMakeLists.txt:82 (target_link_libraries):
Error:   Target "vtpty" links to:

    Libssh2::libssh2

  but the target was not found.

I think, on windows, we need the old way, but then explicitly link against the _static version.

[Yaraslaut]

CMake Error at src/vtpty/CMakeLists.txt:82 (target_link_libraries):
Error:   Target "vtpty" links to:

    Libssh2::libssh2

  but the target was not found.

I think, on windows, we need the old way, but then explicitly link against the _static version.

I reverted this commit