GitHub is reporting some include files as C++ instead of C, and it is reporting
some .pl files as Perl instead of Assembly. Attempt to fix that.
Remove superfluous entries in ./.gitattributes and consolidate some of the
.gitattributes files into ./.gitattributes.
Much of the repetitive logic was put into mk/Common.props,
mk/Windows.props, and mk/WindowsTest.props. There is still a lot of
repetitive logic in the test project files that should be moved to
WindowsTest.props in the future. (In fact, it would be better if the
build system were modified in the future to work like CMake does,
(re-)generating the necessary project files during the build.)
Regular (OPENSSL_NO_ASM) mode will come in a later commit.
I've marked the Visual Studio files as eol=crlf in .gitattributes for
now. This should be the least painful option, since it any CRLF
conversion would create problems for for people sharing a source tree
across platforms (e.g. a shared folder in a VM), and because Visual
Studio IDE resets the files back to CR/LF line endings whenever a
change to project or solution settings is made using its GUI. There is
no license comment in these files because Visual Studio strips comments
when changes are made using the GUI.