a8cas-util.pl

Added primitive wave shapers (option --shape) allowing to choose sine-like or sawtooth-like shape of wawe in output file created during cas -> audio conversion (the default is to create square wave). For turbo formats only.

• Fixed some settings for turbo formats
• Check for existance  of the given input file
• Added optional resonant lowpass filter. It selectively amplifies weak parts of the signal without clipping the rest of it. For now works well with AST format.
• 'pwmc' chunk is now stored according to description
• FSK - fixed detection of "long zeros" in some situations.

• the license was decided (GPLv2)
• possibility to specify checksum type in command line was added; some turbo formats may use more than one algorithm of checksum calculation
• possibility of inverting the signal (--invert) was re-activated
• forgotten description of --mindiff was added to the manual