Support compiling the examples on native Windows without -loldnames.

Support compiling the examples on native Windows without -loldnames.

* gettext-tools/examples/hello-c/configure.ac: Don't test for unistd.h.
* gettext-tools/examples/hello-c-gnome/configure.ac: Likewise.
* gettext-tools/examples/hello-c-gnome3/configure.ac: Likewise.
* gettext-tools/examples/hello-c++/configure.ac: Likewise.
* gettext-tools/examples/hello-c++-qt/configure.ac: Likewise.
* gettext-tools/examples/hello-c++-kde/configure.in.in: Likewise.
* gettext-tools/examples/hello-c++-gnome/configure.ac: Likewise.
* gettext-tools/examples/hello-c++-wxwidgets/configure.ac: Likewise.
* gettext-tools/examples/hello-objc/configure.ac: Likewise.
* gettext-tools/examples/hello-objc-gnome/configure.ac: Likewise.
* gettext-tools/examples/hello-c/hello.c: On native Windows, include <process.h>
and define getpid as an alias of _getpid. Otherwise, assume <unistd.h> exists.
* gettext-tools/examples/hello-c-gnome/hello.c: Likewise.
* gettext-tools/examples/hello-c-gnome3/hello.c: Likewise.
* gettext-tools/examples/hello-c++/hello.cc: Likewise.
* gettext-tools/examples/hello-c++-qt/hello.cc: Likewise.
* gettext-tools/examples/hello-c++-kde/hellowindow.cc: Likewise.
* gettext-tools/examples/hello-c++-gnome/hello.cc: Likewise.
* gettext-tools/examples/hello-c++-wxwidgets/hello.cc: Likewise.
* gettext-tools/examples/hello-objc/hello.m: Likewise.
* gettext-tools/examples/hello-objc-gnome/hello.m: Likewise.