Add tgl-net.c and tgl-timers.c if --enable-libevent is given.
Add gc-section related flags to CFLAGS as well.
Use gc-sections on Linux only.
Remove m4 directory
pytgl: Add tgl-net and tgl-timers to constants.py and mkconstants.py
pytgl: Move everthing required by tgl_init to class __init__ method and make Python API more Pythonic.