Issue title: a _lot_ of strict aliasing warnings
 Issue body: 
# This bug report was migrated from our old Bugzilla tracker.

These attachments are available in the static archive:

* [warnings log (warnings.txt, text/plain, 2018-09-07 08:12:13 +0000, 12615 bytes)](https://bugzilla.libsdl.org/attachment.cgi?id=3300)

**Reported in version:** HG 2.0
**Reported for operating system, platform:** Linux, x86

# Comments on the original bug report:

On 2018-09-07 08:12:13 +0000, Ozkan Sezer wrote:

> Created attachment 3300
> warnings log
> 
> A horde of strict aliasing violation warnings are emitted from joystick
> layer, and also from a few other places. This happens with gcc-4.4.7 on
> Linux CentOS 6.10.  Some other sysjoystick would possibly have the same
> warnings.
> 
> Attached my full log here. Example entry:
> src/joystick/SDL_joystick.c: In function 'SDL_GetJoystickGUIDInfo':
> src/joystick/SDL_joystick.c:1094: warning: dereferencing pointer '({anonymous})' does break strict-aliasing rules

On 2019-05-18 18:48:54 +0000, Ryan C. Gordon wrote:

> 
> Tagging a bunch of bugs with "target-2.0.10" so we have a clear list of things to address before a 2.0.10 release.
> 
> Please note that "addressing" one of these bugs might mean deciding to defer on it until after 2.0.10, or resolving it as WONTFIX, etc. This is just here to tell us we should look at it carefully, and soon.
> 
> If you have new information or feedback on this issue, this is a good time to add it to the conversation, as we're likely to be paying attention to this specific report in the next few days/weeks.
> 
> Thanks!
> 
> --ryan.

On 2019-05-19 18:27:09 +0000, Sam Lantinga wrote:

> Ozkan, do you have a proposed patch for this?

On 2019-05-19 20:13:34 +0000, Ryan C. Gordon wrote:

> 
> For 2.0.10, we can just do -fno-strict-aliasing if this is going to be a problem.

On 2019-05-21 05:05:41 +0000, Ozkan Sezer wrote:

> (In reply to Sam Lantinga from comment # 2)
> > Ozkan, do you have a proposed patch for this?
> 
> Nope. not at the moment.
> 
> (In reply to Ryan C. Gordon from comment # 3)
> > For 2.0.10, we can just do -fno-strict-aliasing if this is going to be a
> > problem.
> 
> Not really a _problem_, just annoyance.

On 2019-05-22 00:38:33 +0000, Sam Lantinga wrote:

> Let's use -fno-strict-aliasing. In my reading it seems like if we don't do that we might have subtle optimization related bugs at any time.

On 2019-06-09 01:33:36 +0000, Sam Lantinga wrote:

> I added -fno-strict-aliasing as a temporary workaround here:
> https://hg.libsdl.org/SDL/rev/1a330416800d
> 
> We can come back to this with real fixes to re-enable these compiler optimizations after 2.0.10 ships.


 Comments: 
 Comment 0: Putting this in 2.0.20 in case we want to revisit (please kick it out of the milestone if we run out of time though).
{'source': 'GithubIssues', 'repo_name_with_owner': 'libsdl-org/SDL', 'issue_id': 806004559, 'repo_stars': 4150.0}