Fix memory leak in DisassemblerX86.
Fix memory leak in DisassemblerX86.

A memory leak in DisassemblerX86 is detected by valgrind. This patch
fixes the DisassemblerX86 destructor to properly free the |current_instr_|
variable.

BUG=471
TEST=Run valgrind on disassembler_x86_unittest to verify the leak is gone.
Review URL: https://breakpad.appspot.com/371001

git-svn-id: a14e546401035be51a469fbea25ecce70a1a22f2@940 4c0a9323-5329-0410-9bdc-e9ce6186880e

tomgr/google-breakpad,tomgr/google-breakpad,tomgr/google-breakpad,tomgr/google-breakpad,tomgr/google-breakpad