Use memchr rather than strchr/index
Use memchr rather than strchr/index

the strings we get from the libvarnishapi functions are not
necessarily null-terminated, so avoid using str* functions on them.

Thanks to lampe for the patch.

Fixes #1115

ajasty-cavium/Varnish-Cache,gauthier-delacroix/Varnish-Cache,alarky/varnish-cache-doc-ja,zhoualbeart/Varnish-Cache,feld/Varnish-Cache,franciscovg/Varnish-Cache,franciscovg/Varnish-Cache,gauthier-delacroix/Varnish-Cache,alarky/varnish-cache-doc-ja,zhoualbeart/Varnish-Cache,chrismoulton/Varnish-Cache,feld/Varnish-Cache,ajasty-cavium/Varnish-Cache,zhoualbeart/Varnish-Cache,1HLtd/Varnish-Cache,gquintard/Varnish-Cache,chrismoulton/Varnish-Cache,ajasty-cavium/Varnish-Cache,feld/Varnish-Cache,feld/Varnish-Cache,mrhmouse/Varnish-Cache,ajasty-cavium/Varnish-Cache,varnish/Varnish-Cache,franciscovg/Varnish-Cache,1HLtd/Varnish-Cache,gquintard/Varnish-Cache,gauthier-delacroix/Varnish-Cache,zhoualbeart/Varnish-Cache,alarky/varnish-cache-doc-ja,gauthier-delacroix/Varnish-Cache,feld/Varnish-Cache,zhoualbeart/Varnish-Cache,mrhmouse/Varnish-Cache,varnish/Varnish-Cache,1HLtd/Varnish-Cache,franciscovg/Varnish-Cache,ajasty-cavium/Varnish-Cache,chrismoulton/Varnish-Cache,franciscovg/Varnish-Cache,gauthier-delacroix/Varnish-Cache,1HLtd/Varnish-Cache,varnish/Varnish-Cache,gquintard/Varnish-Cache,chrismoulton/Varnish-Cache,alarky/varnish-cache-doc-ja,gquintard/Varnish-Cache,chrismoulton/Varnish-Cache,alarky/varnish-cache-doc-ja,mrhmouse/Varnish-Cache,varnish/Varnish-Cache,varnish/Varnish-Cache,mrhmouse/Varnish-Cache,mrhmouse/Varnish-Cache