Add common artifacts to .gitignore.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/21328004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15986 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

.gitignore

@@ -27,12 +27,16 @@ d8
 d8_g
 shell
 shell_g
+/_*
 /build/Debug
 /build/gyp
 /build/ipch/
 /build/Release
+/hydrogen.cfg
 /obj
 /out
+/perf.data
+/perf.data.old
 /test/cctest/cctest.status2
 /test/message/message.status2
 /test/mjsunit/mjsunit.status2
@@ -52,6 +56,7 @@ shell_g
 /tools/oom_dump/oom_dump.o
 /tools/visual_studio/Debug
 /tools/visual_studio/Release
+/v8.log.ll
 /xcodebuild
 TAGS
 *.Makefile
@@ -59,4 +64,3 @@ GTAGS
 GRTAGS
 GSYMS
 GPATH
-/_*