Log Message:
qsynth: Update to 0.6.1

0.6.1  2019-12-22  The Winter'19 Release.

- Custom color (palette) theme editor introduced; color
  (palette) theme changes are now effective immediately,
  except on default.

- Second attempt to fix the yet non-official though
  CMake build configuration.

- When using autotools and ./configure --with-qt=...,
  it is also necessary to adjust the PKG_CONFIG_PATH
  environment variable (after a merge request by plcl
  aka. Pedro López-Cabanillas, while on qmidinet,
  thanks).