Log Message:
Changes 4.6.4:
* NEW Ctrl-Break interrupts fitting run in wgnuplot
* CHANGE treat empty fields in a csv file as "missing" rather than \ 
"bad"
* CHANGE allow reference to more than one column header in 'using' or 'title'
* CHANGE install-info is no longer a default "make install" target
* CHANGE if a polar plot is autoscaled, try to place the origin at the center
* FIX svg and canvas terminal mousing of inverted axis coordinates
* FIX emf failed to initialize font correctly on some systems
* FIX timedata columns can now be referred to via column(N) and \ 
column("HEAD")
* FIX qt terminal toggling of enhanced text elements in plot with labels
* FIX color/pattern generated for key entries of columnstacked histograms
* FIX hitting ^C twice forces temination of wxt session hung by lost X-server
* FIX win terminal failed to properly adjust plot border after window resize
* FIX several conditions in which macros were not expanded during command input
* FIX promote a string containing only digits to INTGR rather than CMPLX
* FIX 'set grid front' caused failure to initialize location of axis zero point
* FIX very poor precision in mouse coords reported by x11 in -persist mode
* FIX parsing of $# (the number of arguments in a "call"). It's not a \ 
comment!
* FIX memory leak of cropped images using pngcairo terminal
* FIX "lc variable" now iterates over linetype colors (not styles) as \ 
documented
* FIX rtics were sometimes drawn with length 0