Apply various fixes and tweaks to Python configuration logic implemented
in the "configure" script:
- Prevent PYTHON_INSTALL_DIR, which holds the value passed to the
--with-python-install-dir option, from being set to "unspec" by
default as this breaks installing Python modules when the
--with-python-install-dir option is not used.
- Make the --with-python-install-dir option also work when the Python
interpreter is specified explicitly (using --with-python=<...>).
- Improve contents and placement of error messages.
- Reduce duplication of code checking Python dependencies.
- Use Autoconf macros AS_CASE() and AS_IF() instead of plain shell
code.
- Update comments. Capitalize the word "Python" when referring to the
language itself rather than a specific executable.
(cherry picked from commit ed4c700c33)
While implementing the new unit testing framework cmocka, it was found that the
BIND 9 code doesn't compile when assertions are disabled or replaced with any
function (such as mock_assert() from cmocka unit testing framework) that's not
directly recognized as assertion by the compiler.
This made the compiler to complain about blocks of code that was recognized as
unreachable before, but now it isn't.
The changes in this commit include:
* assigns default values to couple of local variables,
* moves some return statements around INSIST assertions,
* adds __builtin_unreachable(); annotations after some INSIST assertions,
* fixes one broken assertion (= instead of ==)
(cherry picked from commit fbd2e47f51)
(cherry picked from commit b222783ae9)
