Switch Travis CI environment to Trusty - PHP 5.3 no longer available Sept 2017

[netweb]

Via ​#WP41292

Travis CI have announced they are going to switch to Trusty as the default distro come July 18th 2017

​https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming

Incoming patch will allow us to continue having PHP 5.3 Travis CI jobs until September 2017

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The current availability of PHP 5.3 in the Travis CI build environment is the following:

1. ✅ dist: precise with sudo: false
2. ❌ dist: trusty with sudo: false
3. ❌ dist: precise with sudo: false
4. ❌ dist: precise with sudo: required

BuddyPress' current Travis CI config uses option 1 above
Travis CI will override this configuration with option 2 come July 18th 2017
We can work around this issue for PHP 5.3 until September 2017 using option 3 for the PHP 5.3 Travis CI job
Come September 2017 Travis CI will overwrite option 3 above with option 4

I've created the following Travis CI issue on the subject: ​https://github.com/travis-ci/travis-ci/issues/8072

[netweb]

Updated ticket to remove PHP 5.2 references as BP no longer supports PHP 5.2 :)

[netweb]

In 11634:

Build Tools: Switch to Ubuntu Trusty as the the default linux distro for Travis CI.

• This changeset also explicitly adds dist: precise to the PHP 5.3 build job.
• Travis CI will discontinue support of PHP 5.3 in September 2017 and a further follow up will be required.

Fixes #7567.

[netweb]

In 11635:

Build Tools: Move PHP 5.3 Travis CI job from the php section to the matrix section.

This changeset is a follow up to [11634] where the "build matrix" was broken, my bad.

See #7567.