fix audio rec
Improve exec command processing

- Make exec print out an error if execve() failed for some reason
- Pass init's environment, created by the export keywords, to the exec'd
  command, which is helpful when running shell scripts (for PATH) and/or
  am (for BOOTCLASSPATH) from an exec statement.

Conflicts:
	init/builtins.c
enable STREAM_FM
do not change umask of forked processes to 077