[Feature #1949] Warn needless escaped characters

Feature #1949: Warn needless escaped characters
http://redmine.ruby-lang.org/issues/show/1949

e$B5/I<<Te(B: Yui NARUSE
e$B%9%F!<%?%9e(B: Assigned, e$BM%@hEYe(B: Normal
e$BC4Ev<Te(B: Yui NARUSE, e$B%+%F%4%je(B: core

e$B@55,I=8=Fb$G$NITI,MW$J%(%9%1!<%W$K7Y9p$r=P$7$^$;$s$+!#e(B

e$BF05!$H$7$F$O!“e(B/\uXXXX/e$B$NHs8_49@-$NOC$,$”$j$^$9!#e(B

e$B$3$l$O!"e(BRuby
1.8e$B$K$$$$F!“ITI,MW$J%(%9%1!<%W$G$”$C$?e(B/\u/e$B$,!"e(B
Ruby 1.9e$B$K$
$$$F$Oe(B\uXXXXe$B$H$$$&9=J8$,DI2C$5$l$?$,$?$a$K!"e(B
e$B%(%i!<$,=P$?$j0UL#$,JQ$o$C$F$7$^$C$?$j$7$?$H$$$&OC$G$7$?!#e(B

e$B$3$N$h$&$JIT9,$J=PMh;v$O!"e(B/\u/e$B$H=q$$$?$i7Y9p$r=P$9$h$&$K$7$F$$$?$i!"e(B
e$BL$A3$KKI$0$3$H$,$G$-$?$j!"Ho32$r8:$i$9$3$H$,$G$-$?$+$b$7$l$^$;$s!#e(B

e$B>-Mh$^$?JL$N%(%9%1!<%W5-K!$,DI2C$5$l$k;v$O==J,$"$jF@$kOC$@$H;W$$$^$9!#e(B
e$B$=$N:]$KF1$8IT9,$r7+$jJV$5$J$$$h$&$K!"7Y9p$r=P$9$h$&$K$7$^$;$s$+!#e(B

e$B6qBNE*$K$O!"J8;z%/%i%930$Ne(B
g, i, j, k, l, m, o, p, q, y, E, F, H, I, J, K, L, N, O, P, Q, R, T, U,
V, X, Y
e$B$H!“J8;z%/%i%9Fb$Ne(B
g, i, j, k, l, m, o, p, q, y, z, A, B, E, F, G, H, I, J, K, L, N, O, P,
Q, R, T, U, V, X, Y, Z
e$B$”$?$j$K$J$k$G$7$g$&$+!#e(B

e$B$J$*!“8=>u$G$O7Y9p$,=P$J$$$,!”$9$G$K%(%9%1!<%W5-K!$H$7$FMQ$$$F$$$k!“e(B
/\p/e$B$”$?$j$O5DO@$NM>CO$N$"$k$H$3$m$+$b$7$l$^$;$s!#e(B

e$B%A%1%C%He(B #1949 e$B$,99?7$5$l$^$7$?!#e(B (by Yui NARUSE)

e$B%9%F!<%?%9e(B Assignede$B$+$ie(BClosede$B$KJQ99e(B
e$B?JD=e(B % 0e$B$+$ie(B100e$B$KJQ99e(B

Applied in changeset r24825.

http://redmine.ruby-lang.org/issues/show/1949