1.6 specific tweaks

svn path=/branches/SPIRIT_RC_1_6_2/boost/libs/spirit/; revision=26445
more maintenance
ading a readme.html
more...

svn path=/branches/SPIRIT_RC_1_6_2/boost/libs/spirit/; revision=26460
more maintenance
ading a readme.html
more...

svn path=/branches/SPIRIT_RC_1_6_2/boost/libs/spirit/; revision=26461
tweaks

svn path=/branches/SPIRIT_RC_1_6_2/boost/libs/spirit/; revision=26463
Correcting threads support handling in bjam and tests

svn path=/branches/SPIRIT_RC_1_6_2/boost/libs/spirit/; revision=26478