utils moved to pev
added X_OPEN_SOURCE definition due strdup() use
make: Define _XOPEN_SOURCE only for Cygwin as it breaks on Darwin.
- Probable fix for #64.
  Introduce new option: LIBPE_OPT_OPEN_RW.
  This is used to decide which flags to pass to open(2) and mmap(2).
  For instance, we should only call open(2) with O_RDWR if we have
  permission to write the file we're analyzing. The same applies to
  mmap(2) with MAP_SHARED.
- Fix pe_err_e values. Duh!
Fix support for DESTDIR.
Revert "Fix support for DESTDIR."

This reverts commit 12083cd5548f97618f6587c01c01de816fed2c71.
Makefile: Following Thermi's commit on pev to fix DESTDIR.