gdbproxy

[Robert Lunnon]

On solaris gdbproxy doesn't compile because S_un is not defined, S_un is only 
defined on SOlaris for XPG 4 applications.

The header file however exposed _S_un so should this be _S_un or do I have to 
invent a new test for these features.

Grabbed these comments off the net
POSIX
     Applications that are  intended  to  be  conforming  POSIX.1
     applications  must  define the feature test macros specified
     by the standard before including any headers.  For the stan-
     dards  listed  below,  applications  must define the feature
     test macros listed.   Application  writers  must  check  the
     corresponding standards for other macros that can be queried
     to determine if desired options are supported by the  imple-
     mentation.

POSIX Standard              Feature Test Macros
     POSIX.1-1990                  _POSIX_SOURCE
     POSIX.1-1990 and              _POSIX_SOURCE and
        POSIX.2-1992 C-Language       _POSIX_C_SOURCE=2
        Bindings Option
     POSIX.1b-1993                 _POSIX_C_SOURCE=199309L
     POSIX.1c-1996                 _POSIX_C_SOURCE=199506L

X/Open CAE
     To build or compile an application that conforms to  one  of
     the X/Open CAE specifications, use the following guidelines.
     Applications need not set the POSIX feature test  macros  if
     they require both CAE and POSIX functionality.

XPG3      The application must define _XOPEN_SOURCE  with  a
               value other than 500 (preferably 1).

XPG4      The application must define _XOPEN_SOURCE  with  a
               value  other  than  500  (preferably  1)  and  set
               _XOPEN_VERSION=4.

SUS (XPG4v2)
               The application must define _XOPEN_SOURCE  with  a
               value  other  than  500  (preferably  1)  and  set
               _XOPEN_SOURCE_EXTENDED=1.

SUSv2     The application must define _XOPEN_SOURCE=500.