Merge branch 'next'

* next:
  chore, add travis ci config file
  fix, make sure strerror() exists
  chore, actually check for string.h and strerror()
  chore, save and restore ac_c_werror_flag in sxe-compiler.m4
  minor, provide strerror tool with basic functionality errno -> description
  chore, actually check for gengetopt in c.ac