build gdbserver with -Werror by default

[Pierre Muller]

  Hi Pedro,

  Cygwin 1.7 fails on gdbserver:
gcc -c -Wall -Wdeclaration-after-statement -Wpointer-arith -Wformat-nonliteral -
Werror -gstabs+ -O0    -I. -I../../../src/gdb/gdbserver -I../../../src/gdb/gdbse
rver/../common -I../../../src/gdb/gdbserver/../regformats -I../../../src/gdb/gdb
server/../../include ../../../src/gdb/gdbserver/tracepoint.c
cc1: warnings being treated as errors
../../../src/gdb/gdbserver/tracepoint.c: In function `add_tracepoint_action':
../../../src/gdb/gdbserver/tracepoint.c:1870: error: array subscript has type `c
har'
make[3]: *** [tracepoint.o] Error 1

  isxdigit argument type is int, not char according to man page...
Adding an explicit typecast to int at that line
allows to go to compilation of win32-low.c, but there you
end up with warnings about deprecated functions...
  To fix that, you would need to use the same kind of macros
as in gdb/windows-nat.c

Pierre Muller
Pascal language support maintainer for GDB