minor misleading configure error-msg around PCRE

[e1c1bac6253dc54a1e89ddc046585792 at posteo.net]

Hi,

./configure: error: the HTTP rewrite module requires the PCRE library.
You can either disable the module by using 
--without-http_rewrite_module
option, or install the PCRE library into the system, or build the PCRE 
library
statically from the source with nginx by using --with-pcre=<path> 
option.

This happens when not having pcre, using --without-http_rewrite_module 
BUT
also --with-pcre as an option, like:
./configure --without-http_rewrite_module --with-pcre

For sure that's a stupid combination, but just happened in a very long, 
generated
configure line here. FWIW, this was on OpenBSD 5.1.