Rename relevant global symbols from size to bitlen

Just applying rename.pl with this file:

mbedtls_cipher_get_key_size mbedtls_cipher_get_key_bitlen
mbedtls_pk_get_size mbedtls_pk_get_bitlen
MBEDTLS_BLOWFISH_MIN_KEY MBEDTLS_BLOWFISH_MIN_KEY_BITS
MBEDTLS_BLOWFISH_MAX_KEY MBEDTLS_BLOWFISH_MAX_KEY_BITS
diff --git a/library/pk.c b/library/pk.c
index 5a83855..b5810b5 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -327,7 +327,7 @@
 /*
  * Get key size in bits
  */
-size_t mbedtls_pk_get_size( const mbedtls_pk_context *ctx )
+size_t mbedtls_pk_get_bitlen( const mbedtls_pk_context *ctx )
 {
     if( ctx == NULL || ctx->pk_info == NULL )
         return( 0 );