Avoid assertion failure in VCC if the first symbol encountered in VCL is not an ID
Avoid assertion failure in VCC if the first symbol encountered in VCL is not an ID

Trivial test VCL:

	C{ }C; vcl 4.0;

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