CI: Update Compiler Warnings, Enable Warnings as Errors

[gardner48]

• Additional warning flags from Fix missing statics and dead code identified with -Wmissing-declarations #481, Fix casting warnings identified with -Wcast-qual flag #482, and Fix promotion of double to sunrealtype identified with -Wdouble-promotion #483
• Remove -Wno-deprecated-declarations
• Enable warnings as errors in GitHub actions

[gardner48]

CI failures should be resolved as related PRs are merged

[Steven-Roberts]

When building in single precision, -Wdouble-promotion causes tons of warnings from printf which can't be helped. Maybe it should be added conditionally.

[gardner48]

When building in single precision, -Wdouble-promotion causes tons of warnings from printf which can't be helped. Maybe it should be added conditionally.

Is there a configuration where we could have this flag and avoid the warnings from printf?

[Steven-Roberts]

Is there a configuration where we could have this flag and avoid the warnings from printf?

When precision is set to extended, -Wdouble-promotion is most useful. It's also fine to have the flag when precision is double, but it's not going to identify any promotion warnings.

[gardner48]

When precision is set to extended, -Wdouble-promotion is most useful. It's also fine to have the flag when precision is double, but it's not going to identify any promotion warnings.

Ah yes, the docs only talk about float to double promotion but it makes sense this would for double to long double promotion as well. I'll update this in a sec.