eCos support

This patch does two things:

  1. it adds a define called GTEST_HAS_WCHAR which 
     defaults to 1. This can be set to 0 on platforms
     where wchar_t is unavailable or broken.
  2. it adds a define called GTEST_HAS_SETENV which 
     defaults to 1. his can be set to zero on platforms
     without environment variable support.
  3. it adds a define called GTEST_OS_ECOS which sets
     some GTEST_HAS_* defines necessary for compiling
     under the ecospro operating system.