* Institute a hack for the Sparc call to mmap() to get our generated code to be

  laid out closer to the VM so that calls to library functions (e.g. puts()) and
  callback (e.g.  JITResolver::CompilationCallback) fit into 30 bits of the call
  instruction.
* Abort if architecture is not yet supported (not X86 or Sparc) because it
  likely requires a different set of parameters to mmap() .
* Stop using hard-coded values for page size; use sysconf(_SC_PAGESIZE) instead.

llvm-svn: 6610