Create MBEDTLS_X509_OCSP_PARSE_C feature macro

The new MBEDTLS_X509_OCSP_PARSE_C is a feature macro that can be
controlled from the config.h file to enable/disable the OCSP X509
feature at compile time.

include/mbedtls/check_config.h

@@ -642,6 +642,11 @@
 #error "MBEDTLS_X509_CSR_PARSE_C defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_X509_OCSP_PARSE_C) && ( !defined(MBEDTLS_X509_USE_C) || \
+    !defined(MBEDTLS_X509_CRT_PARSE_C) )
+#error "MBEDTLS_X509_OCSP_PARSE_C defined, but not all prerequisites"
+#endif
+
 #if defined(MBEDTLS_X509_CRT_WRITE_C) && ( !defined(MBEDTLS_X509_CREATE_C) )
 #error "MBEDTLS_X509_CRT_WRITE_C defined, but not all prerequisites"
 #endif

include/mbedtls/config.h

@@ -2518,6 +2518,19 @@
  */
 #define MBEDTLS_X509_CSR_PARSE_C
 
+/**
+ * \def MBEDTLS_X509_OCSP_PARSE_C
+ *
+ * Enable X.509 Online Certificate Status Protocol (OCSP) parsing.
+ *
+ * Module:  library/x509_ocsp.c
+ *
+ * Requires: MBEDTLS_X509_USE_C, MBEDTLS_X509_CRT_PARSE_C
+ *
+ * This module is used for reading X.509 OCSP responses.
+ */
+#define MBEDTLS_X509_OCSP_PARSE_C
+
 /**
  * \def MBEDTLS_X509_CREATE_C
  *

include/mbedtls/x509_ocsp.h

@@ -53,6 +53,7 @@
 #define MBEDTLS_X509_OCSP_CERT_STATUS_REVOKED               1
 #define MBEDTLS_X509_OCSP_CERT_STATUS_UNKNOWN               2
 
+#if defined(MBEDTLS_X509_OCSP_PARSE_C)
 /**
  * \addtogroup x509_module
  * \{
@@ -190,4 +191,6 @@ int mbedtls_x509_ocsp_parse_response_file( mbedtls_x509_ocsp_response *resp,
 }
 #endif
 
+#endif /* MBEDTLS_X509_OCSP_PARSE_C */
+
 #endif /* !MBEDTLS_X509_OCSP_H */

library/x509_ocsp.c

@@ -24,6 +24,8 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#if defined(MBEDTLS_X509_OCSP_PARSE_C)
+
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
@@ -1528,3 +1530,4 @@ int mbedtls_x509_ocsp_parse_response_file( mbedtls_x509_ocsp_response *resp,
 
     return( ret );
 }
+#endif /* MBEDTLS_X509_OCSP_PARSE_C */