Fix player state for unsupported audio file formats

Player thread now sets its status correctly. Closes #360.
Link dynamic pianobar against gcrypt

Commit 96db841a16670b52fa462337c657c6dc6bd2844a added initialization
functions to the pianobar binary but failed to link the dynamically
linked version against libgcrypt. Closes #362.
Makefile: Use new json-c pkgconfig file name

Keeps compatibility with older versions (will be removed in the future).
Closes #364.
Makefile: Use simple variables

TIL recursive variables and $(shell …) slow down `make`.
Merge remote-tracking branch 'promy/master'

Conflicts:
	Makefile