library: Remove signal name from library

Procps library previously held functions that were about either
listing or finding signal names. These are not really the right
location for a library about reading procfs.

This patch handles signal related functions in two ways:

For functions purely found in skill, these have been moved back
into this binary as they are used nowhere else.

For functions used across the binaries, these have been moved
into include/signals.h and lib/signals.c. Besides formatting,
these functions are largely the same.

To assist the skill functions, two functions to access the
signal map array have been added to lib/signals.c

include/signals.h

@@ -0,0 +1,28 @@
+#ifndef PROC_SIG_H
+#define PROC_SIG_H
+/*
+ * Copyright 1998-2003 by Albert Cahalan; all rights resered.
+ * This file may be used subject to the terms and conditions of the
+ * GNU Library General Public License Version 2, or any later version
+ * at your option, as published by the Free Software Foundation.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Library General Public License for more details.
+ */
+
+__BEGIN_DECLS
+
+extern const int number_of_signals;
+
+extern const char *get_sigtable_name(int row);
+
+extern const int get_sigtable_num(int row);
+
+/* return -1 on failure */
+extern int signal_name_to_number(const char *__restrict name);
+
+extern const char *signal_number_to_name(int signo);
+
+__END_DECLS
+#endif