[asan] Fix signal interception on Android.
[asan] Fix signal interception on Android.

All supported version of Android provide both "signal" and
"bsd_signal" libc exports. Binaries built for API level <21 call
bsd_signal; newer binaries call signal.

Simply intercept both.

Fixes AddressSanitizer.SignalTest on Android/x86.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@246716 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt