doc: merged old docs for Enumerable#grep.
doc: merged old docs for Enumerable#grep.

fashionsun/prototype,leafo/prototype,ldf7801528/prototype,erpframework/prototype,erpframework/prototype,292388900/prototype,lamsieuquay/prototype,ldf7801528/prototype,sstephenson/prototype,ShefronYudy/prototype,Gargaj/prototype,Gargaj/prototype,sdumitriu/prototype,ridixcr/prototype,ShefronYudy/prototype,baiyanghese/prototype,ldf7801528/prototype,ShefronYudy/prototype,leafo/prototype,loduis/prototype,fashionsun/prototype,loduis/prototype,erpframework/prototype,sdumitriu/prototype,sstephenson/prototype,sdumitriu/prototype,ridixcr/prototype,Jiasm/prototype,Gargaj/prototype,lamsieuquay/prototype,fashionsun/prototype,Jiasm/prototype,Jiasm/prototype,baiyanghese/prototype,loduis/prototype,292388900/prototype,sstephenson/prototype,292388900/prototype,lamsieuquay/prototype,ridixcr/prototype