Ignore llgo binary/test output
Implement close() builtin
debug: don't generate nil llvm.Value{} if FileDescriptor==""

Fixes an assertion/segfault in LLVM, because we we
do an unconditional ReplaceAllUsesWith to handle
cyclic metadata references.
Implement select via libgo
Merge pull request #132 from axw/libgo-select

Implement select via libgo