Linux brk() syscall returns the new program break

The behavior of the Linux brk() system call is different from the
behavior provided by the glibc wrapper. The actual system call
returns the new program break on success. On failure, the system
call returns the current break.

This change fixes the LSS brk() declaration to match the Linux system
call rather than that of the glibc wrapper.

BUG= none
TEST= none
R=mseaborn@chromium.org

Review URL: https://codereview.chromium.org/22999007

git-svn-id: http://linux-syscall-support.googlecode.com/svn/trunk@22 829466d3-f3f5-3ae4-62ad-de35cf9bba21