Add InitialMmapSize to bolt options

[raskchanky]

https://hashicorp.atlassian.net/browse/VAULT-2552

Since we're rapidly accumulating options that we want to share between raft.db and vault.db, I refactored the freelistOptions() function to be more generally boltOptions(). I'm using strconv.IntSize to determine whether we're on a 32bit or 64bit architecture, since we only want the InitialMmapSize to be set for 64bit platforms. I'm including a few screenshots here of a simple program I wrote to test that this works the way I think it should.

This is the program in its entirety, running locally on my MBP.

This is the same program, running on 32bit Debian Linux, in a VM.

In addition to the program and its output, I also included the output of a few different utilities, in an effort to demonstrate that this VM is really running 32bit Linux.

I also included a few tests, one 32 bit specific, to make sure that we're not setting InitialMmapSize on 32bit platforms.

[ncabatoff]

I don't understand the package build failures, but it's suspicious that all the failing ones are 32-bit targets.

[raskchanky]

@ncabatoff I tried compiling this on my 32bit VM and it errored on this line:
o.InitialMmapSize = 100 * 1024 * 1024 * 1024
saying that it overflows int.

So it appears that I need to re-work this to use platform specific build tags instead.

[raskchanky]

I'm also not sure if this requires a changelog or not, since it's not a user visible change. Thoughts?

[ncabatoff]

I'm also not sure if this requires a changelog or not, since it's not a user visible change. Thoughts?

My position is that if a change affects the compiled binary, it deserves a changelog.

[ncabatoff]

LGTM but you have failing tests