https://bugzilla.gnome.org/show_bug.cgi?id=791121

On ppc archtecture the "nm_bt_vtable_network_server" symbol in the small
objects section instead of .bss, represencted by a "S" letter. Also
include "G" which is an equivalent thing for initialized data. We don't
seem to have such objects at the moment, but when we do it could result
in a nasty surprise.

When building with -flto, we need to use linker plugins.
In case of binutils' nm, it means to prefer gcc-nm if
available.

Like for ranlib and ar, prefer gcc-nm.

- replace AC_PATH_TOOL() by AC_CHECK_TOOLS(). That is consistent
  with what we do for ar,ranlib and suggested on bgo#783311.
- instead of using the variable $BINUTILS_NM, replace it by
  $NM, which is more common according to bgo#783311.
- Keep recognizing $BINUTILS_NM environment, which was introduced
  by commit 8bc88bcc7c. This is purely to keep previous build
  scripts working. Originally I named it "$BINUTILS_NM" because
  using $NM in NetworkManager seemed confusing. But well...

https://bugs.gentoo.org/show_bug.cgi?id=620052
https://bugzilla.gnome.org/show_bug.cgi?id=782525
https://bugzilla.gnome.org/show_bug.cgi?id=783311

Previously, the test runner would only accept leading options,
an optional "--" separator, followed by "$TEST" and optional arguments
for the test.

Like

  ./tools/run-nm-test.sh -m src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh

That is annoying, because to toggle an option you have to seek the
curser in the before the test name.

Now, accept a "--test" option, so that the above can be done with trialing
arguments:

  ./tools/run-nm-test.sh -t src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh -m

However, the arguments for the tests still must come last:

  ./tools/run-nm-test.sh -m [--] src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh -p /settings/plugins/ifcfg-rh/bridge/write-master
  ./tools/run-nm-test.sh -t src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh -m [--] -p /settings/plugins/ifcfg-rh/bridge/write-master

  ./tools/run-nm-test.sh -m src/settings/plugins/ifcfg-rh/tests/test-ifcfg-rh

makes the test before running it. However, that failed if the
test didn't exist already. Reorder the code so that we always
try to make the test before trying to run it.

Also, set pipefail to catch the failures of all components of a
pipeline.

`nm` is used by "tools/create-exports-NetworkManager.sh" script.
Alloc configuring an explicit path during configure.

  BINUTILS_NM=/usr/bin/nm ./configure

Previously, an enum that didn't explicitly specify a numeric value
would wrongly start counting at 1.

E.g.

  typedef enum {
     MY_VAL,
  } Name;

would result in documentation with MY_VAL=1.

https://bugzilla.gnome.org/show_bug.cgi?id=776848

Generating "src/NetworkManager.ver" each time seems to work well.
Thus, src/NetworkManager.ver-orig is unused an gets easily out
of date. Just remove it. It's not useful anymore.

- also when called from makefile, allow enabling valgrind even if it was not
  enabled via configure option. That is, even if you configured --without-valgrind,
  you can run tests via `NMTST_USE_VALGRIND=1 make check`. Previously, there
  was no way to run on valgrind during `make check` unless you also had
  configured --with-valgrind.
- Use $NMTST_VALGRIND variable to override the valgrind path. This now
  always takes precedence. For `make check`, the path can be determined
  by the configure script.
  If all unspecified, as last fallback "valgrind" is searched in the current
  $PATH.
- Allow to specify the suppressions file via $NMTST_SUPPRESSIONS.
  If unset, fall back to the default. The default during `make check`
  is determined by the configure options. The default for manual
  invocation is our one valgrind.suppressions file.
  To use no suppressions file, set NMTST_SUPPRESSIONS to empty.

Now, regardless of what you enabled during ./configure, you can
overwrite it via:

  $ NMTST_USE_VALGRIND=1 \
    NMTST_VALGRIND=~/bin/valgrind \
    NMTST_SUPPRESSIONS=my-suppressions \
    make check