update doc for supported isl versions

       * doc/install.texi: Document supported versions of ISL.

From-SVN: r226211

gcc/ChangeLog

+2015-07-25  Sebastian Pop  <s.pop@samsung.com>
+
+	* doc/install.texi: Document supported versions of ISL.
+
 2015-07-25  Jeff Law  <law@redhat.com>
 
 	Revert:

gcc/doc/install.texi

@@ -383,11 +383,11 @@ installed but it is not in your default library search path, the
 @option{--with-mpc} configure option should be used.  See also
 @option{--with-mpc-lib} and @option{--with-mpc-include}.
 
-@item ISL Library version 0.14 (or 0.12.2)
+@item ISL Library version 0.15, 0.14, 0.13, or 0.12.2
 
 Necessary to build GCC with the Graphite loop optimizations.
-It can be downloaded from @uref{ftp://gcc.gnu.org/pub/gcc/infrastructure/}
-as @file{isl-0.12.2.tar.bz2}.  If an ISL source distribution is found
+It can be downloaded from @uref{ftp://gcc.gnu.org/pub/gcc/infrastructure/}.
+If an ISL source distribution is found
 in a subdirectory of your GCC sources named @file{isl}, it will be
 built together with GCC.  Alternatively, the @option{--with-isl} configure
 option should be used if ISL is not installed in your default library