[PATCH] doc: requirements: reword and readd MPFR URL

[Philippe Blain <levraiphilippeblain@gmail.com>]

In 3401f947d86 (Improve documentation of GDB build requirements and
options, 2023-04-05), the "Requirements" section of the doc was reworked
to reduce repetitions and move MPFR from "Tools/Packages Optional for
Building GDB" to "Tools/Packages Necessary for Building GDB".

In the process, the URL of the MPFR homepage was forgotten. Add it
back.

Also reword slightly the first paragraph of the new  "Libraries"
subsection under "Tools/Packages Necessary for Building GDB".

---
 gdb/doc/gdb.texinfo | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index ea86d49ddab..78bb35939c4 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -39826,9 +39826,9 @@ make program.  Other variants of @code{make} will not work.
 The following libraries are mandatory for building @value{GDBN}.  The
 @file{configure} script searches for each of these libraries in
 several standard locations; if some library is installed in an unusual
-place, you can use the @file{configure} either the option
-@option{--with-@var{lib}} to specify its installation directory, or
-two separate options @option{---with-@var{library}-include} (to
+place, you can use either the @option{--with-@var{lib}}
+@file{configure} option to specify its installation directory, or
+the two separate options @option{---with-@var{library}-include} (to
 specify the location of its header files) and
 @option{--with-@var{library}-lib} (to specify the location of its
 libraries).  For example, for the GMP library, the 3 options are
@@ -39847,7 +39847,8 @@ arithmetics.  The latest version of GMP is available from
 @item MPFR (The GNU Multiple-precision floating-point library)
 @value{GDBN} uses MPFR to emulate the target floating-point
 arithmetics during expression evaluation, if the target uses different
-floating-point formats than the host.
+floating-point formats than the host. The latest version of MPFR is
+available from @url{http://www.mpfr.org}.
 @end table
 
 @end table

---
base-commit: 31c502801798f397d6ec44d081350c704ca4a901
change-id: 20230407-doc-requirements-fixes-322aa70519af
--
b4