Export symbols in common.h file

[Nayef211]

Description

• Define TORCHTEXT_API macro for visibility control #1806 added a TORCHTEXT_API to export relevant symbols on Windows platform
• We add the macro to the methods in common.h as these are used by functions in vocab_factory.h

[Nayef211]

All of the MacOS failures should be fixed by #1886. The Windows unittest failure looks new and will require further investigation but is not caused by this PR.

According to @mthrok, the binary_macos_conda_py3.7 failure happens frequently in torchaudio and is usually ignored by them as they are autoresolved.

[joecummings]

This looks good, thanks for doing this!

One possible nit: I usually squash (fold in the mercurial world) unimportant commits like "Fixing imports" so there's less clutter in the commit history. If this isn't common practice w/ torchtext, no worries, but thought I'd mention it.

[Nayef211]

This looks good, thanks for doing this!

One possible nit: I usually squash (fold in the mercurial world) unimportant commits like "Fixing imports" so there's less clutter in the commit history. If this isn't common practice w/ torchtext, no worries, but thought I'd mention it.

That's a good point. In torchtext, we generally keep all commits (even unimportant ones related to linting), but when we merge we create a PR against the main branch, we always use the "Squash and Merge" option. This way all commits are preserved in the PR/feature branches but commits in the main branch always map 1 to 1 with the corresponding PR. Lmk if this practice makes sense to you, if not we can discuss what the best practice should be moving forward.