Attempting to compile the SPDY patch with the new 1.3.13 release gives:

$ make
make -f objs/Makefile
make[1]: Entering directory `/home/nick/src/nginx-1.3.13'
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
-o objs/src/http/ngx_http_spdy.o \
src/http/ngx_http_spdy.c
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
-o objs/src/http/ngx_http_spdy_filter_module.o \
src/http/ngx_http_spdy_filter_module.c
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
-o objs/src/http/modules/ngx_http_autoindex_module.o \
src/http/modules/ngx_http_autoindex_module.c
cc -c -pipe -O -W -Wall -Wpointer-arith -Wno-unused-parameter -Werror -g -I src/core -I src/event -I src/event/modules -I src/os/unix -I objs -I src/http -I src/http/modules \
-o objs/src/http/modules/ngx_http_auth_basic_module.o \
src/http/modules/ngx_http_auth_basic_module.c
src/http/ngx_http_spdy.c: In function ‘ngx_http_spdy_run_request’:
src/http/ngx_http_spdy.c:1747:33: error: variable ‘fc’ set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors
make[1]: *** [objs/src/http/ngx_http_spdy.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make[1]: Leaving directory `/home/nick/src/nginx-1.3.13'
make: *** [build] Error 2


The patch was applied exactly as specified in the README, with no additional addons. 1.3.12 built with the SPDY patch on the machine without error

Note that I can build 1.3.13 on other machines