Fix compilation if mmap is not reqested

:: upstream revision 10843 ::
Do not use the obsolete getpagesize() function

It may be a macro instead of an actual function call, which is at least undesired.

:: upstream revision 10844 ::
Give a chance to gettext to find whatever it needs

If the included gettext is to be compiled, it requires some tests to be done
before. And since the library is written in C, the tests should also run in C.
Some of them would unconditionally fail in C++ mode.

:: upstream revision 10845 ::