Shrimp Shader Generator FLTK2 GUI (SVN)

FIX: zoom slider wasn't clamped properly

Leave original active>mousepointer (straight) connection line, and commented active>mousepointer spline code - it's there for reference only.

Further tweaks to GUI, rolled up blocks color is consistent with UI theme, width/height ratio for blocks is tweaked (thanks Ben).

Added Ben's spline curve connection lines. Stippled origin>mouse position splines aren't working yet. Width/height ratio changed as well.

Made input pad text (on blocks) scale dependent, now font size scales with zoom level.

Continued tweaking existent blocks so that more meaningful input pad names are used and displayed.

Updated shading functions block to have more meaningful input pad names, small tweaks to the blocks.

All blocks now display their input pad names. Colors tweaked so that input pad names are light blue, hovering orange, together with small UI tweaks that should improve readability. Group names problem fixed, no longer centered, now it's above group widget.

Added aov_opacity AOV to root block source and AOV headers, and Thin Film Interference block (spec6), based on Jens's VEX shader. Tweaked rgb<>spec6 functions for Aqsis workarounds (component access can only be made with (xyz)comp in Aqsis). Both Aqsis and Pixie seem to accept arrays as function arguments, but there are some problems yet with rgb<>spec6 in both Aqsis and Pixie.
Glass block tweaked for Aqsis and Pixie workarounds (component access, array initialization, ternary operator expressions). Added missing vector exponent, maximum, and minimum functions to helpers header.

Added color conversion functions (rgb>spec6>rgb), based on Mario Marengo's VEX functions from his glass shader. Added optics data (Schott catalogue) for glass types, generated by modified mktables.C, also taken from Mario Marengo's glass shader. Changed the glass block so that dispersion in RYGCBV is done optionally if "usespec6" is toggled on, in which case the "ior" variable is ignored in favor of the IOR data taken from the tables, controlled by the "optics" variable (range [0,112]). Tables will get FreeSnell/Sopra n+k data later, color header will get extra color space conversions later as well.