Instead of checking Fcall.data==nil, check Fcall.count==0. The former check always fails after `gcc -O2` optimizations (gcc version 8.3.0). Also fix an out-of-bound read detected by valgrind: ``` ==31162== Invalid read of size 1 ==31162== at 0x11005E: morerules (rules.c:739) ==31162== by 0x110254: writerules (rules.c:775) ==31162== by 0x10D2FE: fsyswrite (fsys.c:848) ==31162== by 0x10C304: fsysproc (fsys.c:248) ==31162== by 0x112E8C: threadstart (thread.c:96) ==31162== by 0x4A682BF: ??? (in /usr/lib/libc-2.29.so) ==31162== Address 0x4ea984a is 0 bytes after a block of size 250 alloc'd ==31162== at 0x483AD7B: realloc (vg_replace_malloc.c:826) ==31162== by 0x1196F3: p9realloc (malloc.c:53) ==31162== by 0x10BDFD: erealloc (plumber.c:124) ==31162== by 0x10FCD9: concat (rules.c:642) ==31162== by 0x10FCD9: concat (rules.c:635) ==31162== by 0x110230: writerules (rules.c:773) ==31162== by 0x10D2FE: fsyswrite (fsys.c:848) ==31162== by 0x10C304: fsysproc (fsys.c:248) ==31162== by 0x112E8C: threadstart (thread.c:96) ==31162== by 0x4A682BF: ??? (in /usr/lib/libc-2.29.so) ``` Fixes #256

According to <https://askubuntu.com/a/309146>, use of `/proc/acpi` to get battery usage is deprecated. This commit replaces the two files from this API with the single file `/sys/class/power_supply/BAT0/capacity`, simultaneously removing the need to calculate battery percentage.

The immediate display of the screen sometimes miss the update from the CPU side memory. No obvious synchronization mechanism is available. In order to make sure the screen updates properly, we set needsDisplay again after 16ms delay to ensure a second screen update.

This supports non-live window resize.

Just as look expands a click in /etc/passwd to the full name (provided that file exists), it now expands a click in https://9fans.net/ to the full URL (provided the prefix is http:// or https://). Probably more adjustment is needed.

Autoident mode is the leading cause of trailing spaces on lines. Remove them during Put to make various picky tools happier. The changes during Put are added as a separate entry to the file history, so that the first Undo after Put restores the spaces.

* devdraw: cocoa metal screen uses a dirty hack to make everything smooth * devdraw: cocoa metal screen uses a layer to make fullscreen applications behave * devdraw: macOS cocoa metal fix resizeimg without img * devdraw: macOS cocoa metal uses blit instead of render We directly use the blit command encoder to copy texture to the framebuffer. We no longer need to compile the metal shader every time the application starts just for rendering a flat 2D surface. * travis: add osx images covering 10.13 and 10.14

The commit that introduced this was pushed accidentally. It is not a good idea to do this. (It breaks programs that think that a clean window means the body matches the on-disk file.)

Some libraries that depend on devdraw don't know about 32x32 cursor -- mainly 9fans.net/go/draw.