Log Message:
Update gnuplot to 5.4.1

Changes in 5.4.1
================
* NEW "with rgbimage" and "with rgbalpha" accept single \ 
column ARGB input
* NEW add toggle in toolbar widget for qt terminal option "ctrl-q"
* NEW keyword "smooth kdensity period <val>"
* NEW time format %tD encodes days relative to time 0
* NEW pm3d quadrangles in 2D projection are clipped smoothly to x and y
* CHANGE gif animation 'optimize' option is deprecated Bugs #1992 #2070 #2348
* CHANGE svg increase coordinate precision to two decimal points Bug #2369
* FIX y autoscaling of default "with filledcurves" #Bug 2294
* FIX placement of mirrored x and y tics in mode 'set view projection ...'
* FIX pm3d lighting calculation for degenerate quadrangles
* FIX botched deprecation of old syntax for "call" arguments Bug #2298 \ 
#2368
* FIX pm3d "depthorder" affects 'set obj polygon' with >4 vertices \ 
Bug #2297
* FIX loss of precision for asin(x), asinh(x) with real x << 0 Bug #2302
* FIX error handling of bad font name in enhanced text Bugs #2303 #2308
* FIX incomplete domain for complex acosh(x), real x < -1 was treated as NaN
* FIX error handling of fuzzed input  Bugs #2306 #2307 #2309 #2312 #2344
* FIX add range check for plot of binned data (allows clipping on y)
* FIX "unzoom" applied to autoscaled volatile data
* FIX no default for binary columns needed if there is a 'using' spec Bug #2315
* FIX buffer overflow of enhanced text fragment  Bugs #2310 #2311
* FIX qnorm and Hann functions applied in dgrid3d Bugs #2277 #2318
* FIX handling of dashtype given as a string with leading whitespace Bug #2336
* FIX preserve key position across isolated instance of "title at x,y" \ 
Bug #2342
* FIX contour labels had spurious point symbols
* FIX allow "pointtype variable" in combination with jitter Bug #2354
* FIX cgm: sanity for non-zero font size Bug #2358
* FIX more checks for valid UTF-8 Bugs #2362 #2364