Add maskHash to RSA_PSS_PARAMS for compat

This CL adds a maskHash member to the rsa_pss_params_st struct for
increased compatibility with OpenSSL: https://source.chromium.org/chromium/chromium/src/+/main:third_party/perl/c/include/openssl/rsa.h;l=282-289

Node.js recently began to make use of this member in https://github.com/nodejs/node/pull/39851
and without this member Electron sees compilation errors.

Change-Id: Ibd18a31605b0a715edb279a3bca4b4f05e679767
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49365
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/include/openssl/base.h b/include/openssl/base.h
index 223c0c5..8be10d1 100644
--- a/include/openssl/base.h
+++ b/include/openssl/base.h
@@ -422,6 +422,7 @@
 typedef struct rand_meth_st RAND_METHOD;
 typedef struct rc4_key_st RC4_KEY;
 typedef struct rsa_meth_st RSA_METHOD;
+typedef struct rsa_pss_params_st RSA_PSS_PARAMS;
 typedef struct rsa_st RSA;
 typedef struct sha256_state_st SHA256_CTX;
 typedef struct sha512_state_st SHA512_CTX;