Some? autoconf tests that include stdio.h fail with a missing ssp.h on cygwin

It looks like ssp doesn't actually work on cygwin. We should fix the ssp test so it includes studio.h and fails.

configure:10546: checking whether the compiler accepts -fstack-protector-all
configure:10565: gcc -c -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -pedantic -Werror -fstack-protector-all  -I${top_srcdir}/src/common conftest.c >&5
configure:10565: $? = 0
configure:10584: gcc -o conftest.exe -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -pedantic -Werror -fstack-protector-all  -I${top_srcdir}/src/common  conftest.c  >&5
configure:10584: $? = 0
configure:10596: result: yes
configure:10622: checking whether the compiler accepts -Wstack-protector
configure:10641: gcc -c -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-all -pedantic -Werror -Wstack-protector  -I${top_srcdir}/src/common conftest.c >&5
configure:10641: $? = 0
configure:10672: result: yes
configure:10685: checking whether the compiler accepts --param ssp-buffer-size=1
configure:10704: gcc -c -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-all -Wstack-protector -pedantic -Werror --param ssp-buffer-size=1  -I${top_srcdir}/src/common conftest.c >&5
configure:10704: $? = 0
configure:10735: result: yes
configure:10749: checking whether the compiler accepts -fPIE
configure:10768: gcc -c -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-all -Wstack-protector --param ssp-buffer-size=1 -pedantic -Werror -fPIE  -I${top_srcdir}/src/common conftest.c >&5
configure:10768: $? = 0
configure:10799: result: yes
configure:10811: checking whether the linker accepts -pie
configure:10854: gcc -o conftest.exe -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-all -Wstack-protector --param ssp-buffer-size=1 -fPIE -pedantic -Werror  -I${top_srcdir}/src/common     -pie conftest.c  -lz  -levent -lssl -lcrypto      >&5
In file included from /usr/include/stdio.h:800,
                 from conftest.c:78:
/usr/local/lib/gcc/x86_64-unknown-cygwin/8.1.0/include/ssp/stdio.h:38:10: fatal error: ssp.h: No such file or directory
 #include <ssp.h>
          ^~~~~~~
compilation terminated.
configure:10854: $? = 1
configure: program exited with status 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME "tor"
| #define PACKAGE_TARNAME "tor"
| #define PACKAGE_VERSION "0.3.3.7"

(similar macros)

| #define STDC_HEADERS 1
| #define HAVE_SYS_TYPES_H 1

(similar macros)

| /* end confdefs.h.  */
| #include <stdio.h>
| int
| main ()
| {
| fputs("", stdout)
|   ;
|   return 0;
| }
configure:10868: result: no