Copy default search path from libXcursor
In 2018, the default search path was changed in libXcursor in commit 2263c196cb0d. Specifically, ~/.local/share/icons was added. This was never copied to xcb-util-cursor. Additionally, libXcursor configures its search path based on e.g. --prefix instead of hardcoding /usr.
This commit brings this library in sync with libXcursor's behaviour.
Since the default value now contains ${datadir}, we have to get that expanded. The previous approach only did one step of expansion, resulting in ${datarootdir}. Thus, the -DXCURSORPATH compiler argument now needs to be generated in Makefile.am to ensure recursive substitution.
This was tested with "make V=1" which showed the following in its output for a run without any flags passed to configure:
"-DXCURSORPATH=\"~/.local/share/icons:~/.icons:/usr/local/share/icons:/usr/local/share/pixmaps\""
Fixes: #12 (closed) Signed-off-by: Uli Schlachter psychon@znc.in