Bug 1078383: update gdbserver to 7.7 to fix the FD leak to the debugged process. r=mwu

Change-Id: I0581df615ab110de82429c051c4b10baf27abd7d
Merge pull request #245 from CervantesYu/gdbserver-7.7-v2.1

Bug 1078383: update gdbserver to 7.7 to fix the FD leak to the debugged. r=mwu, a=bajaj