a couple of tweaks to the Wiki

[Martin Sebor <msebor at redhat dot com>]

I noticed a couple pf problems with glibc installation
instructions on the Wiki. Before I go ahead and change
anything I want to make sure I'm not missing something.

The FAQ named How do I install all of the GNU C Library
project libraries that I just built?
(http://sourceware.org/glibc/wiki/FAQ)
says that make install INSTALLDIR=/tmp/glibc will install
in /tmp/glibc. That's not the case and the prefix the
library was configured with is writeable. There are no
references to INSTALLDIR in glibc. The variable that does
work and that the GNU Coding Standards recommend is DESTDIR.
The standards also recommend prefix and exec_prefix but they
don't work in glibc (that seems like a bug to me and unless
someone lets me know otherwise I'll open one in Bugzilla).

The section titled Building glibc with intent to install on
the Testing/Builds page shows a shell script that makes use
of an INSTALLDIR convenience variable to show how to install
the library to a directory other than prefix. The snippet
exports the variable, suggesting that it's used by some of
the tools invoked by it. Since that's not the case, I would
like to remove the export keyword and change its name to
lowercase to make it clear that the variable has no special
significance.
http://sourceware.org/glibc/wiki/Testing/Builds

I'll go ahead and make these changes unless someone corrects
my understanding or suggests something different.

Thanks
Martin