[icu-support] ICU4C platform porting changes: please test

[Markus S. <mar...@gm...>]

Dear ICU users,

For ICU4C 49, we are changing the way we handle platform support. It is
likely that we have broken platforms where we do not build and test ICU
ourselves.
We did get this to work for Windows, Mac OS, Linux, AIX, Solaris, MinGW,
Cygwin, z/OS and others.

If you have an "unusual" platform or suspect that we might not have your
configuration, then please try out the trunk version of
ICU4C<http://site.icu-project.org/repository>
.
If there is a problem, then please submit a bug report. Include the svn
revision number (e.g., from "svn info") and the relevant parts of the build
and/or test logs. Please also try to fix it for your platform and attach a
patch file (bear in mind that we likely do not have your configuration
available ourselves).

For details please see the quote below from the trunk readme.
See also User Guide: How To Use
ICU<http://userguide.icu-project.org/howtouseicu>
 and ReadMe: Recommended Build
Options<http://source.icu-project.org/repos/icu/icu/trunk/readme.html#RecBuild>

[http://source.icu-project.org/repos/icu/icu/trunk/readme.html#News]
One shared platform.h

ICU4C 49 does not generate any source code files via autoconf any more.
Instead, platform.h itself is now a normal source header file, and
determines platform-specific settings via #if ... etc.

As a result, it is easier to cross-compile ICU4C and/or use different build
systems. No more headers are #included from the build-output directory, and
all platforms use the same set of source code files.

However, it is likely that ICU4C 49 will not compile on some platforms
(non-POSIX and/or older/unusual compilers etc.) that the ICU team did not
test. As a temporary workaround, any platform-dependent macro for which
platform.h does not determine the correct value can be predefined via
CPPFLAGS or by adding an explicit #define ... into platform.h before it
first tests that macro.

Please submit a bug ticket per platform with details about your compiler,
its version and its predefined macros. (For example, preprocessing an empty
source file with gcc's -dM option outputs all of gcc's predefined macros: gcc
-E -dM -x c /dev/null | sort) A patch to fix the problem would be welcome
too!

Thanks and best regards,
markus