Use xreplace instead of subs in Derivative instantiation
Use xreplace instead of subs in Derivative instantiation

Speedup differentiation of expressions by using xreplace instead of
subs.

Shaswat27/sympy,aktech/sympy,Titan-C/sympy,kaichogami/sympy,kevalds51/sympy,yukoba/sympy,MechCoder/sympy,oliverlee/sympy,yashsharan/sympy,jaimahajan1997/sympy,maniteja123/sympy,pandeyadarsh/sympy,lindsayad/sympy,yukoba/sympy,shikil/sympy,Curious72/sympy,souravsingh/sympy,oliverlee/sympy,souravsingh/sympy,ChristinaZografou/sympy,cswiercz/sympy,Curious72/sympy,atreyv/sympy,chaffra/sympy,Designist/sympy,farhaanbukhsh/sympy,moble/sympy,chaffra/sympy,debugger22/sympy,mcdaniel67/sympy,jbbskinny/sympy,saurabhjn76/sympy,MechCoder/sympy,ahhda/sympy,yukoba/sympy,Davidjohnwilson/sympy,emon10005/sympy,wanglongqi/sympy,Titan-C/sympy,Titan-C/sympy,shikil/sympy,ga7g08/sympy,Davidjohnwilson/sympy,pandeyadarsh/sympy,hargup/sympy,cswiercz/sympy,Vishluck/sympy,rahuldan/sympy,yashsharan/sympy,sampadsaha5/sympy,skidzo/sympy,drufat/sympy,kaushik94/sympy,oliverlee/sympy,abhiii5459/sympy,postvakje/sympy,sahmed95/sympy,jaimahajan1997/sympy,Arafatk/sympy,AkademieOlympia/sympy,sampadsaha5/sympy,rahuldan/sympy,ChristinaZografou/sympy,lindsayad/sympy,AkademieOlympia/sympy,kaichogami/sympy,iamutkarshtiwari/sympy,madan96/sympy,Vishluck/sympy,ga7g08/sympy,jbbskinny/sympy,hargup/sympy,Vishluck/sympy,mafiya69/sympy,emon10005/sympy,saurabhjn76/sympy,wanglongqi/sympy,Shaswat27/sympy,maniteja123/sympy,yashsharan/sympy,drufat/sympy,debugger22/sympy,atreyv/sympy,Davidjohnwilson/sympy,chaffra/sympy,shikil/sympy,cswiercz/sympy,atreyv/sympy,mcdaniel67/sympy,Curious72/sympy,MechCoder/sympy,kevalds51/sympy,rahuldan/sympy,wanglongqi/sympy,mcdaniel67/sympy,postvakje/sympy,abhiii5459/sympy,sampadsaha5/sympy,aktech/sympy,mafiya69/sympy,jerli/sympy,saurabhjn76/sympy,Arafatk/sympy,drufat/sympy,ahhda/sympy,ChristinaZografou/sympy,madan96/sympy,iamutkarshtiwari/sympy,pandeyadarsh/sympy,VaibhavAgarwalVA/sympy,kaushik94/sympy,ga7g08/sympy,VaibhavAgarwalVA/sympy,Designist/sympy,maniteja123/sympy,Designist/sympy,madan96/sympy,kaichogami/sympy,moble/sympy,jerli/sympy,farhaanbukhsh/sympy,iamutkarshtiwari/sympy,moble/sympy,skidzo/sympy,kevalds51/sympy,kaushik94/sympy,lindsayad/sympy,jaimahajan1997/sympy,farhaanbukhsh/sympy,skidzo/sympy,VaibhavAgarwalVA/sympy,jerli/sympy,sahmed95/sympy,AkademieOlympia/sympy,emon10005/sympy,abhiii5459/sympy,postvakje/sympy,debugger22/sympy,Shaswat27/sympy,sahmed95/sympy,Arafatk/sympy,hargup/sympy,mafiya69/sympy,ahhda/sympy,jbbskinny/sympy,souravsingh/sympy,aktech/sympy