Update install.texi for GCC 6 on Solaris

Update install.texi for GCC 6 on Solaris

	* doc/install.texi (Specific, i?86-*-solaris2.10): Update gas and
	gld requirements.
	(Specific, *-*-solaris2*): Update Solaris 11 bundled gcc
	versions.
	Mention Solaris 11 packaging changes.
	Update gas and gld requirements.
	Remove reference to pre-Solaris 10 bug.
	(Specific, sparc-sun-solaris2*): Remove reference to pre-Solaris 10
	systems and bugs.
	(Specific, sparc64-*-solaris2*): Remove reference to bootstrap
	with cc.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-6-branch@235163 138bc75d-0d04-0410-961f-82ee72b054a4