saugns v0.3.9. Anti-aliasing. Wave, ramp, math changes. Fixes.

Correct some irregularities in syntax handling
including most noticeably the O 'c' parameter,
now behaving like other parameters (instead of
the last value set to an object on a line with
several objects being applied to all objects).

Rework oscillator for some real anti-aliasing.
Remove old "rounding" from 'sqr', 'saw' waves,
use one level of DPW-like pre-integrated table
for all wave types (and FM, PM) in oscillator.

Extend num. expr. syntax, recognizing built-in
math functions which are now usable as part of
specifying arguments for numerical parameters.

Rework design from an earlier version and peel
off some complexity without functional change.

Correct and expand README on amplitude modulation;
describe ring modulation, also supported using the
AM syntax since early 2011 versions.

Wave types:
 * Rename:
    - 'sha' -> 'ahs' (absolute half-frequency sine).
    - 'szh' -> 'hrs' (half-rectified sine).
    - 'ssr' -> 'srs' (square root of sine).
 * Add:
    - 'ssr' (squared & square root of sine).

Ramp types:
 * Rename:
    - 'esd' -> 'xpe' (eXPonential Envelope).
    - 'lsd' -> 'lge' (LoGarithmic Envelope).
 * Add:
    - 'cos' (cos-like increase or decrease).

Math functions:
 * Add:
    - abs(x)  Absolute value.
    - exp(x)  Base-e exponential value.
    - log(x)  Natural logarithmic value.
    - sqrt(x) Square root.
    - met(x)  Metallic value.

Also add test script for using pre-existing features
to get an "IXA synthesis" sound.
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