jsoncons: skip a few tests with libstdc++, fix 32-bit

[barracuda156]

Description

This is a header-only port, but it is set to build tests by default. A number of tests are broken on systems using libstdc++.
Also -Werror breaks 32-bit build.
Fix both issues.

There is no change to the headers, only conditional skipping of broken tests and dropping of -Werror on 32-bit archs.

Remaining tests appear to pass.

Discussion with upstream: danielaparker/jsoncons#488

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 10.6
Xcode 3.2

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint --nitpick?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@sikmir for port jsoncons.