Fixed line/column numbers in math expr/ops error messages. Updated tests.
Merge pull request #1714 from seven-phases-max/math-op-error-msg-fix

Fix for math expr/ops error messages line/column numbers.
More consistent named color variables (preserve color string on output when possible).
More consistent named color variables: fixed color name output with --compress option
More consistent named color variables: optimized numeric to named color conversions, updated tests.
color-string-var: updated `color` function, updated tests
color-string-var: fixed `color` function, fixed tests
color-string-var: changed "named color" indication method, now we

simply store the original keyword within color object to get rid of all
that  gray<->grey, fuchsia<->magenta and aqua<->cyan conflicts.