try out tracing on *BSD and Solaris

add tests for tracing static binaries

trace static children of static children

inject errors into trace when violation occurs rather than kill the child

cache results of filesystem checks

review erealpath vs realpath usage

add tests to make sure errno is saved/restored properly

wrappers for execl{,l,p} ... unfortunately, we'll probably have to basically
reimplement the functions (building up argv[] and then call the execv* ver)

erealpath() might deref symlinks when working with unreadable paths as non-root
even when working on funcs that do not deref funcs themselves ... this isnt a
real big issue though

threaded apps conflict with shared state:
 - sandbox_lib
 - sandbox_on
 - trace_pid
 - etc...

doesnt seem to work quite right:
	echo $(./vfork-0 ./mkdir_static-0 2>&1)