Fixes #2482

And also add proj_context_errno_string()

Revise gie 'expect failure errno XXXX' strings

Gone are pj_malloc, pj_calloc, pj_dalloc and pj_dealloc. Their primary
function as API memory functions in proj_api.h is no longer there and
the other use as a workaround for old errno problems is no longer valid
either.

Replaced with malloc and free across the codebase.

Should hopefully result in no change in results, and hopefully more
readable code...

This is mostly to have better OSSFuzz report. Currently a lot
of bug summaries are like
`proj4/standard_fuzzer: Divide-by-zero in s_inverse`

By prefixing the projection name, we will get better reports, like
`Divide-by-zero in airy_s_inverse`

This also makes it slightly easier to set a breakpoint by
function name.

The one-point case was completely broken with lat_0 being ignored.
I've fixed that, and also modified the alpha orientation, so that the angle
corresponds to the one of the 2 point case when going from point 1 to point 2,
similarly to what omerc does.
This was found rather experimentaly with the added test cases that try to
find equivalence between 1-point and 2-point cases.

Fixes #1379
and adresses https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13930

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11699
Credit to OSS Fuzz