Enable preedit color on external preedit window with x11 applications.

BUG=http://code.google.com/p/ibus/issues/detail?id=1731
TEST=ui/gtk3/ibus-ui-gtk3

Review URL: https://codereview.appspot.com/119480043
Do not fail ibus-setup when en_US.UTF-8 is not installed.

BUG=https://code.google.com/p/ibus/issues/detail?id=1740
TEST=setup

Review URL: https://codereview.appspot.com/136080043
Fix compose keys in French layout bepo variant.

fr(bepo) sends dead_currency with Shift+AltGr+e and
ibus should send currency with dead_currency+dead_currency but
gtkimcontextsimpleseqs.h was not sorted in the descending order
and failed to get dead_currency.
Also need to add dead_stroke and dead_belowcomma for
AltGr+l and Shift+AltGr+Cedilla

BUG=https://code.google.com/p/ibus/issues/detail?id=1742
TEST=src/libibus.so

Review URL: https://codereview.appspot.com/135470043
Update translations.

Update as.po ko.po pl.po

Review URL: https://codereview.appspot.com/141980043
Release 1.5.9

Review URL: https://codereview.appspot.com/141950044