Tests: a couple of auxiliary environment variables introduced.

lib/Test/Nginx.pm

diff --git a/lib/Test/Nginx.pm b/lib/Test/Nginx.pm
index b010276..1f88e53 100644
--- a/lib/Test/Nginx.pm
+++ b/lib/Test/Nginx.pm
@@ -348,6 +348,9 @@
 	$s .= "pid $self->{_testdir}/nginx.pid;\n";
 	$s .= "error_log $self->{_testdir}/error.log debug;\n";
 
+	$s .= $ENV{TEST_NGINX_GLOBALS}
+		if $ENV{TEST_NGINX_GLOBALS};
+
 	$self->{_test_globals} = $s;
 }
 
@@ -375,6 +378,9 @@
 	$s .= "scgi_temp_path $self->{_testdir}/scgi_temp;\n"
 		if $self->has_module('scgi');
 
+	$s .= $ENV{TEST_NGINX_GLOBALS_HTTP}
+		if $ENV{TEST_NGINX_GLOBALS_HTTP};
+
 	$self->{_test_globals_http} = $s;
 }