* idSysSignal::Wait should now handle timeouts > 1s better (or at all)
* Use clock_gettime for Sys_Milliseconds()
* Use CLOCK_MONOTONIC_RAW (and CLOCK_MONOTONIC as fallback if
that's not available) for Sys_Milliseconds() and Sys_Microseconds()
CLOCK_MONOTONIC can behave strange when NTP is used
* Small fixes in Sys_Microseconds(): use 64bit int to store time
(like return type...), divide by 1000 (not 1000000) for nsec=>musec
Turned out that as "extension" (which is really more like a pattern
that matches the whole file) was even used with patterns like "*.*"
so we do proper matching using fnmatch() now - which is even easier
than the old way.
Now deleting savegames on POSIX works.
In Sys_ListFiles() the extension was abused to match whole
filenames (of savegames), not just their extensions - that
didn't work with the POSIX backend, now it does.
Sys_ListFiles() now also supports "*" as a wildcard that matches
all files - needed for deleting savegames.
However, things like "bl*" or "*ub" don't work.
While at it, I replaced readdir() with the thread-safe readdir_r()
