Fixes nfc_drivers memory leak
Fix stack smash bug in LOG_HEX() macro

Fixes issue 232
pn53x-tamashell: allow larger commands up to full extended frame (264 bytes)

It was arbitrarily limited to MAX_FRAME_LEN-10 probably because of bug in LOG_HEX() fixed in previous commit
Makefile.am: move header files from noinst_HEADERS to _SOURCES

Ensures proper recompilation when a header file is edited.
cf https://www.gnu.org/software/automake/manual/html_node/Headers.html
make style
Fix warnings: ignoring return value of 'pipe' & discarding const qualifier
Make it possible to disable conf.

Now the configure script has --disable-conf command-line argument
that can be used to turn off environment variables and use of
configuration files.
Split --disable-conf into --disable-conffiles & --disable-envvars
Fix warning in tests: Variable might get clobbered by 'longjmp' or 'vfork'