[minor] capture_client.c: -Wshadow warning

[jpka-]

Hello. I've noted that when i compile capture_client.c with -Wshadow gcc key, i have

warning: declaration of ‘nframes’ shadows a global declaration [...]

while it works just fine.
P.S. The complete command is (looks like -Wshadow is not included in -Wall)

gcc -Wshadow -Wall `pkg-config --cflags --libs jack sndfile` -o capture_client ./capture_client.c

Thanks.