Add LV2 header location compatibility

Update clone URI

Add icon

Announce required LV2 feature (URID map for MIDI)

Work around clang++ 6.x - 7.0.0 complex_t issues

These are empirically only relevant on Apple and FreeBSD. with clang++
6 and 7. Debian's clang++3.8 (stable) as well as clang++-7 (7.0.1 sid)
are fine.

Unify Makefile with other projects: optimization, visibility, etc

Unify shared spectrum/bandpass filter code - fixes freeBSD builds

This code is used in meters.lv2, tuna.lv2 and onsettrigger.lv2.

Fix duplicate version definition (hardcoded + autogenerated)

fix .ttl (missing semicolon)

allow to override STRIP with env variable