Add support for QNX Neutrino part2

pqnx.h was not added in the previous CL by mistake
( ).

A spurious tab in icu.gyp was removed.

README.chromium was updated to clarify how pqnx.h was generated.
platform.qnx.patch was made against a copy of plinux.h

TEST=icu is built properly on qnx. After DEPS roll, net_unittests:*IDN* and base_unittests:*String* all pass on qnx.`

Review URL:

git-svn-id: 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
5 files changed