Add #include <signal.h> to fix the build on linux.  From Eric Wong <normalperson@yhbt.net>
Add #include <signal.h> to fix the build on linux.  From Eric Wong <normalperson@yhbt.net>

yghannam/ffi,yghannam/ffi,tduehr/ffi,majioa/ffi,majioa/ffi,tduehr/ffi,ffi/ffi,MikaelSmith/ffi,tduehr/ffi,mvz/ffi,sparkchaser/ffi,mvz/ffi,ferventcoder/ffi,ffi/ffi,majioa/ffi,MikaelSmith/ffi,ferventcoder/ffi,MikaelSmith/ffi,sparkchaser/ffi,ferventcoder/ffi,yghannam/ffi,mvz/ffi,mvz/ffi,yghannam/ffi,sparkchaser/ffi,yghannam/ffi,tduehr/ffi,ferventcoder/ffi,ffi/ffi,MikaelSmith/ffi,majioa/ffi,sparkchaser/ffi