Fix siginterrupt() deprecation warning on Linux #243

Job	Run time
Apache2 tests on Linux	2m 10s
Apache2 tests on Linux	2m 55s
C++ tests on Linux	1m 23s
C++ tests on Linux	3m 11s
Apache2 tests on macOS	2m 20s
Apache2 tests on macOS	5m 12s
C++ tests on macOS	4m 10s
C++ tests on macOS	4m 37s
Homebrew packaging tests	6m 39s
Homebrew packaging tests	6m 18s
Nginx tests on Linux	2m 16s
Nginx tests on Linux	3m 19s
Nginx dynamic module tests on Linux	1m 5s
Nginx dynamic module tests on Linux	2m 14s
Nginx tests on macOS	3m 2s
Nginx tests on macOS	3m 37s
Nginx dynamic module tests on macOS	1m 15s
Nginx dynamic module tests on macOS	1m 26s
Node.js tests on Linux	22s
Node.js tests on Linux	26s
Ruby tests on Linux	1m 6s
Ruby tests on Linux	1m 53s
Node.js tests on macOS	25s
Node.js tests on macOS	24s
Ruby tests on macOS	1m 10s
Ruby tests on macOS	1m 21s
Passenger Standalone tests on Linux	3m 53s
Passenger Standalone tests on Linux	4m 18s
Source packaging tests	36s
Source packaging tests	24s
Passenger Standalone tests on macOS	4m 51s
Passenger Standalone tests on macOS	5m 45s
	1h 24m 3s

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