Add support for symbol table in .com files

This change fixes minor bugs and adds a feature, which lets us store the
ELF symbol table, inside the ZIP directory. We use the path /zip/.symtab
which can be safely removed using a zip editing tool, to make the binary
smaller after compilation. This supplements the existing method of using
a separate .com.dbg file, which is still supported. The intent is people
don't always know that it's a good idea to download the debug file. It's
not great having someone's first experience be a crash report, that only
has numbers rather than symbols. This will help fix that!

tool/net/help.txt

@@ -58,6 +58,8 @@ FLAGS
   -P PATH   pid file location
   -U INT    daemon set user id
   -G INT    daemon set group id
+  --strace  enables system call tracing
+  --ftrace  enables function call tracing
 
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