Identifiers starting with an underscore and followed immediately by a capital letter are reserved by the C++ standard.
The only header guards not fixed are those in the headers auto-generated from java.
These functions are intended for compatibility with legacy software,
and are not normally needed in new secp256k1 applications.
They also do not obeying any particular standard (and likely cannot
without without undermining their compatibility), and so are a
better fit for contrib.
Unbraced statements spanning multiple lines has been shown in many
projects to contribute to the introduction of bugs and a failure
to catch them in review, especially for maintenance on infrequently
modified code.
Most, but not all, of the existing practice in the codebase were not
cases that I would have expected to eventually result in bugs but
applying it as a rule makes it easier for other people to safely
contribute.
I'm not aware of any such evidence for the case with the statement
on a single line, but some people strongly prefer to never do that
and the opposite rule of "_always_ use a single line for single
statement blocks" isn't a reasonable rule for formatting reasons.
Might as well brace all these too, since that's more universally
acceptable.
[In any case, I seem to have introduced the vast majority of the
single-line form (as they're my preference where they fit).]
This also removes a broken test which is no longer needed.
