tests/generated: Use #if instead of #ifdef

This patch makes the generated tests use #if instead of #ifdef, as it is more
generic and can allow for more complex expressions that will be needed in
future tests.

It also updates the existing tests to make use of it.
tests/generated: Fix pread's configuration header

This patch fixes pread's configuration header, just for aesthetical purposes
(it's not actually used at the moment).
tests/generated: Add a test for strdup()

This patch adds an auto-generated test for strdup().

Note overriding strdup() does not work on some platforms where the libc
defines it as a macro; the test accounts for that and will be skipped with a
warning in those cases.
Do not use the dummy backtrace on profiling builds

When building with PROFILE=1, the current USE_DUMMY_BACKTRACE test fails
because the compiler tries to write to /dev/null.gcno.

This patch fixes it by making it write to a local file instead, which we then
not use.

It also adds the profiling files to .gitignore while at it.
tests: Add a few basic tests

Looking at the test coverage, there were a few simple things that the existing
tests were not covering; this patch fixes some of those by adding a couple of
basic but useful tests.
utils/fiu-ctrl: Remove non-existent -l option from the documentation
libfiu: Add a tracing mode to help debugging

This patch adds two tracing printf()s that are only enabled when using
"make TRACE=1". They can be very useful for debugging issues, and the code
complexity impact is minimal.
tests: Introduce tests/utils

This patch introduces basic tests for the command-line utilities (fiu-run,
fiu-ls, fiu-ctrl).

They are not intended to cover all of libfiu's capabilities, but mostly check
remote control handling from those utilities.
bindings/python: Add a fiu_ctrl.py module

This patch adds a new Python module, fiu_ctrl.py, which implements similar
functionality to the fiu-run and fiu-ctrl shell utilities, but it can be used
from within Python to control tests.
preload/posix: Remove profile-generated files on "make clean"