gcc/
       * attribs.c moved out attribute registration into register_attribute
       * doc/plugins.texi Documented register_attribute and PLUGIN_ATTRIBUTES
       * gcc-plugin.h Added forward decl for register_attribute
       * plugin.c Added PLUGIN_ATTRIBUTES boilerplate
       * plugin.h Added PLUGIN_ATTRIBUTES

gcc/testsuite/
       * g++.dg/plugin/attribute_plugin-test-1.C Testcase input for custom attributes and decl smashing
       * g++.dg/plugin/attribute_plugin.c Testcase plugin to test user attributes
       * g++.dg/plugin/dumb_plugin.c Fixed typo
       * g++.dg/plugin/plugin.exp Added attribute_plugin test

From-SVN: r147516