Silence compiler warnings

- Comparisons between signed and unsigned
- Unused parameter

produced by gcc -Wall -Wextra

picocom.c

@@ -1558,6 +1558,8 @@ loop(void)
 void
 deadly_handler(int signum)
 {
+    (void)signum; /* silence unused warning */
+
     if ( ! sig_exit ) {
         sig_exit = 1;
         kill(0, SIGTERM);

term.c

@@ -244,7 +244,7 @@ struct baud_codes {
 #endif /* of HIGH_BAUD */
 };
 
-#define BAUD_TABLE_SZ (sizeof(baud_table) / sizeof(baud_table[0]))
+#define BAUD_TABLE_SZ ((int)(sizeof(baud_table) / sizeof(baud_table[0])))
 
 int
 term_baud_up (int baud)

term.h

@@ -167,7 +167,8 @@ enum parity_e {
     P_EVEN,
     P_ODD,
     P_MARK,
-    P_SPACE
+    P_SPACE,
+    P_ERROR = -1
 };
 
 /*
@@ -184,7 +185,8 @@ enum flowcntrl_e {
     FC_NONE = 0,
     FC_RTSCTS,
     FC_XONXOFF,
-    FC_OTHER
+    FC_OTHER,
+    FC_ERROR = -1
 };
 
 /*