Log Message:
Updated libsigsegv to 2.11.

Set LICENSE.

New in 2.11:

* Added support for catching stack overflow on Linux/SPARC.

* Provide a correct value for SIGSTKSZ on 64-bit AIX and on HP-UX. The one
  defined by these systems is too small.

* Updated build infrastructure.

* Compilation now requires the <stdint.h> include file. Platforms which
  don't have this include file (such as IRIX) are no longer supported.

* NOTE: Support for Cygwin and native Windows is currently not up-to-date.