As discussed in !455: remove duplicate testing, testing header and
testing the library are a same test in one (for instance we don't want
to get into weird cases where the lib is found but not the header; this
updated test takes such inconsistencies into account). Also it's better
to have all dependency tests together in the root meson file.
Finally adding some comments to make this all more understandable for
anyone looking at this in the future.
More of the files were wrong, or at least not absolutely identical to
the files generated by the autotools. I am not doing any code change
other than trying to make both build systems produce identical files
(except for slight differences on 2 files not worth the effort) even
though maybe some things can be improved (especially on the include
list). Maybe to be improved later.
Also fixing 2 of the previously autotools-generated files because of
space typos which should have been committed earlier.
Finally it is to be noted that there is no logics to copy the generated
files back to the source directory in the meson rules. I am not sure
anyway this is really worth it and maybe we should just stop tracking
these generated files eventually.