tomoyo: automatically use patterns for several situations in learning mode

The "file_pattern" keyword was used for automatically recording patternized
pathnames when using the learning mode. This keyword was removed in TOMOYO
2.4 because it is impossible to predefine all possible pathname patterns.

However, since the numeric part of proc:/$PID/ , pipe:[$INO] and
socket:[$INO] has no meaning except $PID == 1, automatically replacing
the numeric part with \$ pattern helps reducing frequency of restarting
the learning mode due to hitting the quota.

Since replacing one digit with \$ pattern requires enlarging string buffer,
and several programs access only $PID == 1, replace only two or more digits
with \$ pattern.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>