g_str_has_prefix: don't call strlen(str)
g_str_has_prefix: don't call strlen(str)

There's no reason to check the length of @str in g_str_has_prefix(),
since if it's shorter than @prefix, the strncmp() will fail anyway.
And besides making the function less efficient, it also breaks code
like:

    if (buf->len >=3 && g_str_has_prefix (buf->data, "foo"))
      ...

which really looks like it ought to work whether buf->data is
nul-terminated or not.

https://bugzilla.gnome.org/show_bug.cgi?id=727890

Distrotech/glib,ieei/glib,krichter722/glib,lukasz-skalski/glib,mzabaluev/glib,gale320/glib,tchakabam/glib,lukasz-skalski/glib,tchakabam/glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,krichter722/glib,cention-sany/glib,ieei/glib,johne53/MB3Glib,mzabaluev/glib,tchakabam/glib,tchakabam/glib,cention-sany/glib,tamaskenez/glib,krichter722/glib,tamaskenez/glib,ieei/glib,lukasz-skalski/glib,MathieuDuponchelle/glib,tchakabam/glib,johne53/MB3Glib,lukasz-skalski/glib,cention-sany/glib,johne53/MB3Glib,MathieuDuponchelle/glib,johne53/MB3Glib,gale320/glib,endlessm/glib,MathieuDuponchelle/glib,cention-sany/glib,tamaskenez/glib,Distrotech/glib,Distrotech/glib,MathieuDuponchelle/glib,mzabaluev/glib,endlessm/glib,Distrotech/glib,mzabaluev/glib,MathieuDuponchelle/glib,lukasz-skalski/glib,krichter722/glib,endlessm/glib,ieei/glib,gale320/glib,mzabaluev/glib,ieei/glib,tamaskenez/glib,gale320/glib,tamaskenez/glib,krichter722/glib,gale320/glib,endlessm/glib,cention-sany/glib,Distrotech/glib