o remove panic() in favor of err(3) and use err(3) functions
consistently throughout
o use stat(2)'s S_IS* macros rather than S_IF*
o [r]index -> str[r]chr
o convert some static buffers to dynamic ones
o use real tempfiles rather than reopening the same templates
o rename some functions that clash with libc
o convert wait_status from union to int and use wait(2) status macros
o fix multiple potential buffer overflows
o fix a few comments
o add $FreeBSD$
Reviewed by: nra, nectar (earlier version)
popen(), but worse. The child calls execvp(), which calls malloc()
a bit more than execl(), and it calls non-library functions that call
malloc() and who-knows-what else (stdio is called in at least some
error cases).
