Rename identifiers containing double-underscore
Rename identifiers containing double-underscore (`__`) to avoid `__`.
The reason to avoid double-underscore is that all identifiers
containing double-underscore are reserved in C++. Rename all such
identifiers that appear in any public header, including ssl_internal.h
which is in principle private but in practice is installed with the
public headers.
This commit makes check-names.sh pass.
```
perl -i -pe 's/\bMBEDTLS_SSL__ECP_RESTARTABLE\b/MBEDTLS_SSL_ECP_RESTARTABLE_ENABLED/g; s/\bMBEDTLS_KEY_EXCHANGE_(_\w+)_(_\w+)\b/MBEDTLS_KEY_EXCHANGE${1}${2}/g' include/mbedtls/*.h library/*.c programs/*/*.c scripts/data_files/rename-1.3-2.0.txt tests/suites/*.function
```
diff --git a/scripts/data_files/rename-1.3-2.0.txt b/scripts/data_files/rename-1.3-2.0.txt
index cb3381a..e599ac5 100644
--- a/scripts/data_files/rename-1.3-2.0.txt
+++ b/scripts/data_files/rename-1.3-2.0.txt
@@ -706,9 +706,9 @@
POLARSSL_KEY_EXCHANGE_RSA_ENABLED MBEDTLS_KEY_EXCHANGE_RSA_ENABLED
POLARSSL_KEY_EXCHANGE_RSA_PSK MBEDTLS_KEY_EXCHANGE_RSA_PSK
POLARSSL_KEY_EXCHANGE_RSA_PSK_ENABLED MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED
-POLARSSL_KEY_EXCHANGE__SOME__ECDHE_ENABLED MBEDTLS_KEY_EXCHANGE__SOME__ECDHE_ENABLED
-POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED
-POLARSSL_KEY_EXCHANGE__WITH_CERT__ENABLED MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED
+POLARSSL_KEY_EXCHANGE__SOME__ECDHE_ENABLED MBEDTLS_KEY_EXCHANGE_SOME_ECDHE_ENABLED
+POLARSSL_KEY_EXCHANGE__SOME__PSK_ENABLED MBEDTLS_KEY_EXCHANGE_SOME_PSK_ENABLED
+POLARSSL_KEY_EXCHANGE__WITH_CERT__ENABLED MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED
POLARSSL_KEY_LENGTH_DES MBEDTLS_KEY_LENGTH_DES
POLARSSL_KEY_LENGTH_DES_EDE MBEDTLS_KEY_LENGTH_DES_EDE
POLARSSL_KEY_LENGTH_DES_EDE3 MBEDTLS_KEY_LENGTH_DES_EDE3