Avoid left-shifting integers into the sign bit, which is undefined.

Found with UndefinedBehaviorSanitizer.

src/core/ngx_string.c

diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index cf665a4..7a73ef5 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -1563,7 +1563,7 @@
         n = 0;
 
         while (size) {
-            if (escape[*src >> 5] & (1 << (*src & 0x1f))) {
+            if (escape[*src >> 5] & (1U << (*src & 0x1f))) {
                 n++;
             }
             src++;
@@ -1574,7 +1574,7 @@
     }
 
     while (size) {
-        if (escape[*src >> 5] & (1 << (*src & 0x1f))) {
+        if (escape[*src >> 5] & (1U << (*src & 0x1f))) {
             *dst++ = '%';
             *dst++ = hex[*src >> 4];
             *dst++ = hex[*src & 0xf];

src/http/modules/ngx_http_log_module.c

diff --git a/src/http/modules/ngx_http_log_module.c b/src/http/modules/ngx_http_log_module.c
index df9424f..c42fb08 100644
--- a/src/http/modules/ngx_http_log_module.c
+++ b/src/http/modules/ngx_http_log_module.c
@@ -1000,7 +1000,7 @@
         n = 0;
 
         while (size) {
-            if (escape[*src >> 5] & (1 << (*src & 0x1f))) {
+            if (escape[*src >> 5] & (1U << (*src & 0x1f))) {
                 n++;
             }
             src++;
@@ -1011,7 +1011,7 @@
     }
 
     while (size) {
-        if (escape[*src >> 5] & (1 << (*src & 0x1f))) {
+        if (escape[*src >> 5] & (1U << (*src & 0x1f))) {
             *dst++ = '\\';
             *dst++ = 'x';
             *dst++ = hex[*src >> 4];

src/http/modules/ngx_http_userid_filter_module.c

diff --git a/src/http/modules/ngx_http_userid_filter_module.c b/src/http/modules/ngx_http_userid_filter_module.c
index 1487c09..0dbacba 100644
--- a/src/http/modules/ngx_http_userid_filter_module.c
+++ b/src/http/modules/ngx_http_userid_filter_module.c
@@ -836,7 +836,7 @@
     ngx_gettimeofday(&tp);
 
     /* use the most significant usec part that fits to 16 bits */
-    start_value = ((tp.tv_usec / 20) << 16) | ngx_pid;
+    start_value = (((uint32_t) tp.tv_usec / 20) << 16) | ngx_pid;
 
     return NGX_OK;
 }

src/http/ngx_http_parse.c

diff --git a/src/http/ngx_http_parse.c b/src/http/ngx_http_parse.c
index 59aa1fe..bd6c9c9 100644
--- a/src/http/ngx_http_parse.c
+++ b/src/http/ngx_http_parse.c
@@ -481,7 +481,7 @@
         /* check "/.", "//", "%", and "\" (Win32) in URI */
         case sw_after_slash_in_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 state = sw_check_uri;
                 break;
             }
@@ -540,7 +540,7 @@
         /* check "/", "%" and "\" (Win32) in URI */
         case sw_check_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 break;
             }
 
@@ -626,7 +626,7 @@
         /* URI */
         case sw_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 break;
             }
 
@@ -1131,7 +1131,7 @@
         /* check "/.", "//", "%", and "\" (Win32) in URI */
         case sw_after_slash_in_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 state = sw_check_uri;
                 break;
             }
@@ -1179,7 +1179,7 @@
         /* check "/", "%" and "\" (Win32) in URI */
         case sw_check_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 break;
             }
 
@@ -1228,7 +1228,7 @@
         /* URI */
         case sw_uri:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 break;
             }
 
@@ -1289,7 +1289,7 @@
 
         case sw_usual:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 *u++ = ch;
                 ch = *p++;
                 break;
@@ -1358,7 +1358,7 @@
 
         case sw_slash:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 state = sw_usual;
                 *u++ = ch;
                 ch = *p++;
@@ -1401,7 +1401,7 @@
 
         case sw_dot:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 state = sw_usual;
                 *u++ = ch;
                 ch = *p++;
@@ -1442,7 +1442,7 @@
 
         case sw_dot_dot:
 
-            if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+            if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
                 state = sw_usual;
                 *u++ = ch;
                 ch = *p++;
@@ -1836,7 +1836,7 @@
             continue;
         }
 
-        if (usual[ch >> 5] & (1 << (ch & 0x1f))) {
+        if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
             continue;
         }