Fix warnings when compiling on MS-Windows with -std=gnu99.

Fix warnings when compiling on MS-Windows with -std=gnu99.

 src/makefile.w32-in ($(BLD)/w32.$(O)):
 ($(BLD)/vm-limit.$(O)):
 ($(BLD)/term.$(O)):
 ($(BLD)/unexw32.$(O)):
 ($(BLD)/fileio.$(O)):
 ($(BLD)/dispnew.$(O)): Update dependencies.
 src/w32term.h (w32_initialize_display_info, initialize_w32_display):
 Add prototypes.
 src/w32proc.c: Include ctype.h.
 src/w32.h (init_environment, check_windows_init_file)
 (syms_of_ntproc, syms_of_ntterm, dostounix_filename)
 (unixtodos_filename, init_winsock, srandom, random, sys_pipe)
 (set_process_dir, sys_spawnve, register_child, sys_sleep, getwd)
 (sys_link): Add prototypes.
 src/w32.c: Include w32select.h.
 (sys_access, e_malloc, sys_select): Add prototypes.
 (emacs_gnutls_pull): 'timeout' is now EMACS_TIME, not struct timeval.
 src/vm-limit.c [WINDOWSNT]: Include w32heap.h.
 src/unexw32.c: Include lisp.h and w32.h.
 src/term.c [WINDOWSNT]: Include w32term.h.
 src/process.c [WINDOWSNT]: Add prototype of sys_select.
 src/fileio.c [WINDOWSNT]: Include w32.h.
 src/dispnew.c [WINDOWSNT]: Include w32.h.

 nt/inc/pwd.h (getuid, geteuid): Add prototypes.
 nt/inc/ms-w32.h (sys_wait, _getpid, gmtgime_r, localtime_r)
 (signal_handler, sys_signal, sigemptyset, sigfillset, sigprocmask)
 (pthread_sigmask, sigismember, setpgrp, sigaction, alarm)
 (sys_kill, getpagesize): Add prototypes for emulated functions.
 nt/inc/grp.h (getgid, getegid): Add prototypes.
 nt/gmake.defs (DEBUG_CFLAGS) [NOOPT]: Add -std=gnu99.
 nt/configure.bat (chkapiN): Avoid compiler warning in junk.c when
 compiling with -std=gnu99.
 nt/config.nt (CHECK_LISP_OBJECT_TYPE): Don't undef, so that it
 could be used via --cflags switch to configure.bat.