Add C API (#5072)

sdk-c/cbindgen.toml

@@ -0,0 +1,29 @@
+language = "C"
+header = '''// Copyright 2018 Solana Labs, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//
+// Warning, this file is autogenerated by cbindgen. Don't modify this manually.
+'''
+include_version = true
+include_guard = "SOLANA_H"
+tab_width = 4
+documentation_style = "c99"
+
+[parse]
+parse_deps = true
+include = ["solana-sdk"]
+
+[export]
+item_types = ["enums", "structs", "unions", "typedefs", "opaque", "functions"]