adjust installation docs to discourage installing GMP, MPFR and MPC separately

[Gerald Pfeifer]

On Sat, 4 Feb 2012, Jonathan Wakely wrote:
>        * doc/install.texi (Prerequisites): Suggest building GMP, MPFR and
>        MPC as part of GCC before describing configuring with --with-gmp etc.
>        (Installing GCC: Configuration): State that --with-gmp etc. aren't
>        needed if sources are present.

For the ChangeLog I would just say "--with-gmp etc. are not needed
if...", omitting the "State that" which is implied for docs.

+subdirectory of your GCC sources named @file{gmp}, it will be built
+together with GCC, this avoids the need to build GMP separately.
+Alternatively, if GMP is already installed but it is not in your

How about "GCC(full stop). This avoids the need", that is, making
the latter a sentence of its own?  Or just omit this?

Same for the other two libraries.

-If you do not have GMP (the GNU Multiple Precision library), the MPFR
-library and/or the MPC library installed in a standard location and
-you want to build GCC, you can explicitly specify the directory where
+If you want to build GCC but do not have GMP (the GNU Multiple Precision
+library), the MPFR library and/or the MPC library installed in a
+standard location and don't have their sources present in the GCC
+source tree then you can explicitly specify the directory where

"don't" -> "do not"

And I would avoid the expansion of GMP in parenthesis, given how late
we are in the document and all the prior uses.  I acknowledge this
predates you changes, but while we are at it. :-)

The patch is fine with these changes.

Thank you!

Gerald