Internal md5 and sha1 implementations are now always used.

This reduces the number of moving parts in ABI compatibility checks.
Additionally, it also allows to use OpenSSL in FIPS mode while still
using md5 for non-security tasks.

auto/modules

@@ -101,7 +101,6 @@ fi
 
 
 if [ $HTTP_CACHE = YES ]; then
-    USE_MD5=YES
     have=NGX_HTTP_CACHE . auto/have
     HTTP_SRCS="$HTTP_SRCS $HTTP_FILE_CACHE_SRCS"
 fi
@@ -522,8 +521,6 @@ if [ $HTTP_AUTH_REQUEST = YES ]; then
 fi
 
 if [ $HTTP_AUTH_BASIC = YES ]; then
-    USE_MD5=YES
-    USE_SHA1=YES
     have=NGX_CRYPT . auto/have
 
     ngx_module_name=ngx_http_auth_basic_module
@@ -682,7 +679,6 @@ fi
 
 if [ $HTTP_PROXY = YES ]; then
     have=NGX_HTTP_X_FORWARDED_FOR . auto/have
-    #USE_MD5=YES
 
     ngx_module_name=ngx_http_proxy_module
     ngx_module_incs=
@@ -772,8 +768,6 @@ if [ $HTTP_BROWSER = YES ]; then
 fi
 
 if [ $HTTP_SECURE_LINK = YES ]; then
-    USE_MD5=YES
-
     ngx_module_name=ngx_http_secure_link_module
     ngx_module_incs=
     ngx_module_deps=