autoconf macro so generate pthread compiler flags // Re: Child panics on OpenSolaris

[Nils Goroll]

(repost to varnish-cache.org. Sorry, haven't adapted the new domain yet)

> Fantastic. Thank you for putting so much effort into this.
> 
> But also: Stupid I didn't think about this. See how I'm compiling varnish since 
> I started working with it:
> 
> ## 64bit
> LDFLAGS="-lpthread"
> CFLAGS="-D_REENTRANT -m64" \
> VCC_CC="exec gcc -fpic -D_REENTRANT -m64 -shared -o %o %s" \
> ./configure \
> 	'--enable-debugging-symbols' \
> 	'--enable-developer-warnings' \
> 	'--enable-dependency-tracking' \
> 	....

I've tried to automate this configuration in configure.ac.

See: http://varnish-cache.org/ticket/663

Nils