This patch (2nd of 4) includes various changes to Ada related C files required for DJGPP support

ChangeLog entry:

2016-07-30 Andris Pavenis <andris.pavenis@iki.fi>

     * ada/ctrl_c.c: Do not use macro SA_RESTART for DJGPP.

     * ada/gsocket.h: Do not support sockets for DJGPP.

     * ada/init.c (timestruct_t): Define for DJGPP.
       (nanosleep): Implement for DJGPP using usleep().
       (__gnat_install_handler): Implememt for DJGPP

     * ada/sysdep.c: Include <io.h> for DJGPP
       (_setmode): Define to setmode for DJGPP
       (__gnat_set_mode): Add implementation for DJGPP
       (__gnat_localtime_tzoff): Add implementation for DJGPP

     * ada/terminals.c: Add DJGPP to list of unsupported platforms.


Andris