INSTALL: fix compiler detection on FreeBSD+clang (#177)

devdraw: set displaydpi on devdraw x11 attach (#178) See https://plan9port-review.googlesource.com/c/plan9/+/1470 for discussion of the approach, especially Michael Stapleberg's comment: Note that chromium, firefox and others have tried this and then switched to using the Xft.dpi X resource, see e.g. https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/libgtk2ui/gtk2_ui.cc and especially http://sources.debian.net/src/gnome-settings-daemon/3.18.2-1/plugins/xsettings/gsd-xsettings-manager.c/?hl=824#L80 for some anecdata about why this approach doesn’t work out. The Xft.dpi resource is being set accurately by desktop environments (GNOME, KDE, …) and can easily be changed by users of niche window managers by editing ~/.Xresources. I suggest we check only Xft.dpi, without considering the DPI environment variable or the monitor width/height.

mac/9term.app: invoke 9term with -l This seems to match Terminal. Fixes #145.

9term: make 9term -l invoke $SHELL with -l

web: allow any $BROWSER Fixes #118.

fontsrv: increase x11 font height scale (#111)

9term.app: add $PLAN9/bin to $PATH if not already in $PATH (#144) 9term set $PLAN9 if PLAN9 is not set. But $PATH is not set. As a result, 9term exits with "exec devdraw: No such file or directory"

plumb/basic: avoid wrap around in file:1:2 (#158) Fixes #122, #140. As reported in #122, `file:1:1` moves to the end of the file, and `file:1:2` fails with “address out of range”. I’ll use file:2:3 as an example so we can tell the line and column number apart. What’s happening is this: plumb/basic matches `2:3` using twocolonaddr (from plumb/fileaddr), then sets addr to `2-#1+#3` (the 1 is constant and was introduced because column numbers are 1-based). Acme interprets this in three steps: 1. find the range (q0, q1) that contains line 2 2. create the range (q2, q2) where q2 = q0 - 1 3. create the range (q3, q3) where q3 = q2 + 3 The second step has a branch where if q0 == 0 and 1 > 0 (remember that 1 is constant and comes form plumb/basic), q0 is set to the end of the file. This makes addressing things at the end of the file easier. The problem then is that if we select line 1, which starts at the beginning of the file, q0 is always 0 and the branch in step 2) will always be used. `1:1` is interpreted as `1-#1+#1` which starts at 0, wraps around to the end of the file, then moves 1 character backwards and then forwards again, ending at the end of the file. `1:2` is interpretes as `1-#1+#2` which starts at 0, wraps around to the end od the file, then moves 1 character backwards and tries moving 2 characters forwards beyond the end of the file, resulting in the out of range error. In #140 @rsc proposed transforming `:X:Y` into `:X-#0+#Y-#1` instead since that avoids wrapping around by not moving backwards at first. This change modifies `plumb/basic` to do that.

devdraw: make ctrl generate 1-click while mouse down (#119) This makes 2-1 chords possible with touchpad on a mac laptop.

keyboard: add compose sequences lc and rc for ceiling brackets (#126) Change-Id: Ice1c8c9d15cc6febf32dc2b7c449d457acc319b6

keyboard: add tab/untab symbols (#160)

fontsrv: x11 uses FC_POSTSCRIPT_NAME (#174) This makes fontsrv use the PostScript font names on X11. The PostScript font names contains only alphanumeric and hyphens. This allows us to use the Font command in acme. It also matches the font names used by fontsrv on macOS, which has been using PostScript font names.

acme: avoid division by zero when resizing col (#189) To reproduce, create a column with at least two windows and resize acme to have almost zero height.

fontsrv: disable font smoothing on osx (#196) macOS Mojave version 10.14 starts to disable font smoothing. We disable font smoothing for OSX_VERSION >= 101400 to match the system default font rendering. It also makes the font rendering on macOS similar to that on X11.

9term: fix getpts on FreeBSD 11.2 (#199) Opening /dev/ptyXX files fails on recent FreeBSD versions. Following the same fix being applied to Linux, OpenBSD, and Darwin, we use openpty to open a pseudoterminal in openpts.