libre2.symbols: add destructor
libre2.symbols: add destructor

Suggested by Paweł Hajdan

R=rsc
CC=phajdan, re2-dev
https://codereview.appspot.com/11179043

driskell/re2-1,ElectronicRU/re2,yanqingmen/re2,wanggchongg/re2,wanggchongg/re2,ElectronicRU/re2,bowlofstew/re2,yanqingmen/re2,lnussbaum/re2,yanqingmen/re2,wanggchongg/re2,google/re2,AtnNn/re2,evilmucedin/re2,AtnNn/re2,Cfretz244/re2,ElectronicRU/re2,evilmucedin/re2,rAntonioh/re2,google/re2,lnussbaum/re2,rAntonioh/re2,evilmucedin/re2,pombredanne/re2,lnussbaum/re2,pombredanne/re2,driskell/re2-1,AtnNn/re2,simudream/re2,evilmucedin/re2,driskell/re2-1,google/re2,rAntonioh/re2,ElectronicRU/re2,pombredanne/re2,yanqingmen/re2,Cfretz244/re2,lnussbaum/re2,Cfretz244/re2,yanqingmen/re2,AtnNn/re2,driskell/re2-1,google/re2,ElectronicRU/re2,evilmucedin/re2,simudream/re2,wanggchongg/re2,rAntonioh/re2,pombredanne/re2,bowlofstew/re2,bowlofstew/re2,wanggchongg/re2,simudream/re2,Cfretz244/re2,bowlofstew/re2,simudream/re2,pombredanne/re2,bowlofstew/re2,Cfretz244/re2,google/re2,rAntonioh/re2,lnussbaum/re2,driskell/re2-1,AtnNn/re2,simudream/re2