Fixed regex captures handling without PCRE.

If PCRE is disabled, captures were treated as normal variables in
ngx_http_script_compile(), while code calculating flushes array length in
ngx_http_compile_complex_value() did not account captures as variables.
This could lead to write outside of the array boundary when setting
last element to -1.

Found with AddressSanitizer.

src/http/ngx_http_script.c

diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index bff9525..c2b1658 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -350,11 +350,9 @@
                 goto invalid_variable;
             }
 
-#if (NGX_PCRE)
-            {
-            ngx_uint_t  n;
-
             if (sc->source->data[i] >= '1' && sc->source->data[i] <= '9') {
+#if (NGX_PCRE)
+                ngx_uint_t  n;
 
                 n = sc->source->data[i] - '0';
 
@@ -371,9 +369,13 @@
                 i++;
 
                 continue;
-            }
-            }
+#else
+                ngx_conf_log_error(NGX_LOG_EMERG, sc->cf, 0,
+                                   "using variable \"$%c\" requires "
+                                   "PCRE library", sc->source->data[i]);
+                return NGX_ERROR;
 #endif
+            }
 
             if (sc->source->data[i] == '{') {
                 bracket = 1;

src/stream/ngx_stream_script.c

diff --git a/src/stream/ngx_stream_script.c b/src/stream/ngx_stream_script.c
index edf6e89..8130f92 100644
--- a/src/stream/ngx_stream_script.c
+++ b/src/stream/ngx_stream_script.c
@@ -282,11 +282,9 @@
                 goto invalid_variable;
             }
 
-#if (NGX_PCRE)
-            {
-            ngx_uint_t  n;
-
             if (sc->source->data[i] >= '1' && sc->source->data[i] <= '9') {
+#if (NGX_PCRE)
+                ngx_uint_t  n;
 
                 n = sc->source->data[i] - '0';
 
@@ -297,9 +295,13 @@
                 i++;
 
                 continue;
-            }
-            }
+#else
+                ngx_conf_log_error(NGX_LOG_EMERG, sc->cf, 0,
+                                   "using variable \"$%c\" requires "
+                                   "PCRE library", sc->source->data[i]);
+                return NGX_ERROR;
 #endif
+            }
 
             if (sc->source->data[i] == '{') {
                 bracket = 1;