CrashReporter: Show termination signal

...in both text (using strsignal) and numeric form.
Closes SerenityOS#4775.

Applications/CrashReporter/main.cpp

@@ -45,6 +45,7 @@
 #include <LibGUI/LinkLabel.h>
 #include <LibGUI/TextEditor.h>
 #include <LibGUI/Window.h>
+#include <string.h>
 
 static String build_backtrace(const CoreDump::Reader& coredump)
 {
@@ -87,6 +88,7 @@ int main(int argc, char** argv)
  String backtrace;
  String executable_path;
  int pid { 0 };
+ u8 termination_signal { 0 };
 
  {
  auto coredump = CoreDump::Reader::create(coredump_path);
@@ -98,6 +100,7 @@ int main(int argc, char** argv)
  backtrace = build_backtrace(*coredump);
  executable_path = String(process_info.executable_path);
  pid = process_info.pid;
+ termination_signal = process_info.termination_signal;
  }
 
  auto app = GUI::Application::construct(argc, argv);
@@ -147,7 +150,7 @@ int main(int argc, char** argv)
  app_name = af->name();
 
  auto& description_label = *widget.find_descendant_of_type_named<GUI::Label>("description");
- description_label.set_text(String::formatted("\"{}\" (PID {}) has crashed!", app_name, pid));
+ description_label.set_text(String::formatted("\"{}\" (PID {}) has crashed - {} (signal {})", app_name, pid, strsignal(termination_signal), termination_signal));
 
  auto& executable_link_label = *widget.find_descendant_of_type_named<GUI::LinkLabel>("executable_link");
  executable_link_label.set_text(LexicalPath::canonicalized_path(executable_path));