Update references to ICU 5.2 in README.chromium to 5.4

Update references to ICU 5.2 in README.chromium to 5.4

R=jshin@chromium.org
BUG=none

[jochen (gone - plz use gerrit), 2015-02-26 15:39:14]

jochen@chromium.org changed reviewers:
+ machenbach@chromium.org

[jochen (gone - plz use gerrit), 2015-02-26 15:39:14]

I tried and failed to build the windows dll using those instructions. could you
build one please (and update the instructions accordingly)?

V8 depends on icudt.dll for the standalone builds

[jochen (gone - plz use gerrit), 2015-02-26 15:45:56]

the failure is

28>  Building icu data from E:\src\icu54\source\data\in\icudt54l.dat
28>  	cd "E:\src\icu54\source\data\out\build\icudt54l"
28>  	"E:\src\icu54\bin\icupkg" -x * --list
"E:\src\icu54\source\data\in\icudt54l.dat" >
"E:\src\icu54\source\data\out\tmp\icudata.lst"
28>  Item brkitr/en_US_POSIX.res depends on missing item brkitr/word_POSIX.brk
28>  Item coll/id_ID.res depends on missing item coll/id.res
28>  Item coll/in.res depends on missing item coll/id.res
28>  Item lang/mo.res depends on missing item lang/ro_MD.res
28>NMAKE : fatal error U1077: '"E:\src\icu54\bin\icupkg"' : return code '0x2'
28>  Stop.

[jungshik at Google, 2015-03-02 06:52:13]

On 2015/02/26 15:45:56, jochen (traveling) wrote:
> the failure is
> 
> 28>  Building icu data from E:\src\icu54\source\data\in\icudt54l.dat
> 28>  	cd "E:\src\icu54\source\data\out\build\icudt54l"
> 28>  	"E:\src\icu54\bin\icupkg" -x * --list
> "E:\src\icu54\source\data\in\icudt54l.dat" >
> "E:\src\icu54\source\data\out\tmp\icudata.lst"
> 28>  Item brkitr/en_US_POSIX.res depends on missing item brkitr/word_POSIX.brk
> 28>  Item coll/id_ID.res depends on missing item coll/id.res
> 28>  Item coll/in.res depends on missing item coll/id.res
> 28>  Item lang/mo.res depends on missing item lang/ro_MD.res
> 28>NMAKE : fatal error U1077: '"E:\src\icu54\bin\icupkg"' : return code '0x2'
> 28>  Stop.

Thank you for catching them. I know the causes of those errors. 
I'll fix them.

[jungshik at Google, 2015-03-02 09:04:49]

On 2015/03/02 06:52:13, Jungshik at google wrote:
> On 2015/02/26 15:45:56, jochen (traveling) wrote:
> > the failure is
> > 
> > 28>  Building icu data from E:\src\icu54\source\data\in\icudt54l.dat
> > 28>  	cd "E:\src\icu54\source\data\out\build\icudt54l"
> > 28>  	"E:\src\icu54\bin\icupkg" -x * --list
> > "E:\src\icu54\source\data\in\icudt54l.dat" >
> > "E:\src\icu54\source\data\out\tmp\icudata.lst"
> > 28>  Item brkitr/en_US_POSIX.res depends on missing item
brkitr/word_POSIX.brk
> > 28>  Item coll/id_ID.res depends on missing item coll/id.res
> > 28>  Item coll/in.res depends on missing item coll/id.res
> > 28>  Item lang/mo.res depends on missing item lang/ro_MD.res
> > 28>NMAKE : fatal error U1077: '"E:\src\icu54\bin\icupkg"' : return code
'0x2'
> > 28>  Stop.
> 
> Thank you for catching them. I know the causes of those errors. 
> I'll fix them.

See https://codereview.chromium.org/962643003/