runtime: Fix __go_symbol_value val argument to backtrace_syminfo.
runtime: Fix __go_symbol_value val argument to backtrace_syminfo.

R=iant
CC=gofrontend-dev
https://golang.org/cl/6625063

qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,golang/gofrontend,golang/gofrontend,qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,anlhord/gofrontend,qskycolor/gofrontend,anlhord/gofrontend,qskycolor/gofrontend