Fix signal handler signature for GCC 15 compatibility
Fix compilation error on Fedora 43 with GCC 15.2.1. Modern GCC versions treat incompatible pointer types as errors rather than warnings.
The sigWinchCallback function signature was incompatible with the signal() function requirements. Signal handlers must accept an int parameter.
Changed in dump1090.c and view1090.c: void sigWinchCallback() to: void sigWinchCallback(int sig)
Fixes: error: passing argument 2 of 'signal' from incompatible pointer type
Tested on: Fedora 43, GCC 15.2.1