Experimental standard library

Change import syntax and cover with tests

libstdlib/CMakeLists.txt

@@ -0,0 +1,18 @@
+# This will re-generate the headers if any file within src was modified.
+set_directory_properties(PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_SOURCE_DIR}/stdlib/src/)
+
+set(STDLIB stub)
+set(GENERATED_STDLIB_HEADERS)
+foreach(src IN LISTS STDLIB)
+    set(STDLIB_FILE ${CMAKE_SOURCE_DIR}/libstdlib/src/${src}.sol)
+    file(READ ${STDLIB_FILE} STDLIB_FILE_CONTENT HEX)
+    string(REGEX MATCHALL ".." STDLIB_FILE_CONTENT "${STDLIB_FILE_CONTENT}")
+    list(REMOVE_ITEM STDLIB_FILE_CONTENT "0d")
+    string(REGEX REPLACE ";" ",\n\t0x" STDLIB_FILE_CONTENT "${STDLIB_FILE_CONTENT}")
+    set(STDLIB_FILE_CONTENT "0x${STDLIB_FILE_CONTENT}")
+    set(STDLIB_FILE_NAME ${src})
+    configure_file("${CMAKE_SOURCE_DIR}/libstdlib/stdlib.src.h.in" ${CMAKE_BINARY_DIR}/include/libstdlib/${src}.h NEWLINE_STYLE LF @ONLY)
+    list(APPEND GENERATED_STDLIB_HEADERS ${CMAKE_BINARY_DIR}/include/libstdlib/${src}.h)
+endforeach()
+
+configure_file("${CMAKE_SOURCE_DIR}/libstdlib/stdlib.h.in" ${CMAKE_BINARY_DIR}/include/libstdlib/stdlib.h NEWLINE_STYLE LF @ONLY)

libstdlib/src/stub.sol

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity >=0.0;
+
+pragma experimental solidity;
+
+function identity(uint256 x) pure returns (uint256)
+{
+  return x;
+}

libstdlib/stdlib.h.in

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <map>
+#include <string>
+
+#include "libstdlib/stub.h"
+
+namespace solidity::stdlib
+{
+
+static std::map<std::string, std::string> sources = {
+	{ "std.stub", stub }
+};
+
+} // namespace solidity::stdlib

libstdlib/stdlib.src.h.in

@@ -0,0 +1,13 @@
+// The generation of this file is defined in stdlib/CMakeLists.txt.
+// This file was generated by using the content of stdlib/src/@STDLIB_FILE_NAME@.sol.
+
+#pragma once
+
+namespace solidity::stdlib
+{
+
+static char const @STDLIB_FILE_NAME@[] = {
+	@STDLIB_FILE_CONTENT@, 0
+};
+
+} // namespace solidity::stdlib