playlist/extm3u: strip first line for #EXTM3U detection
util/StaticFifoBuffer: make Shift() public
TextInputStream: manually shift the buffer before reading

Fixes truncated lines in m3u and cue files (regression by commit
67958f7).
release v0.19.1
configure.ac: prepare for 0.19.2
pcm/PcmConvert: make AudioFormat parameters "const"
pcm/PcmConvert: assign {src,dest}_format at the end

Fixes assertion failure in destructor by not assigning
{src,dest}_format when an error occurs.
pcm/FormatConverter: move check to Open()

Report unsupported format while opening the filter, not later when the
first conversion takes place.
pcm/ChannelsConverter: fix variable used to generate error message

Use the "_format" parameter instead of the (uninitialized) "format"
attribute.
output/roar: remove unnecessary "volatile" keyword

A mutex acts as a memory barrier, and thus "volatile" is not
necessary.