Avoid misleading special characters within lambda synthetic class names

Enough code in cbmc and its users relies on method names having the form
'java::package.Class.method:(type)' that the existing method for synthesising
lambda class names, which could yield things like java::synthetic_lambda$main:()V$0.<init>,
could cause problems when that colon character in the middle of the name was mistaken
for the function name's trailing type information. Similarly we might end up
needing to append fake type information to the <init> and apply symbol names to
appear "normal" enough.

Author: smowton

jbmc/src/java_bytecode/lambda_synthesis.cpp

@@ -24,13 +24,25 @@ Author: Diffblue Ltd.
 
 #include <string.h>
 
+static std::string escape_symbol_special_chars(std::string input)
+{
+  for(auto &c : input)
+  {
+    if(c == '$' || c == ':' || c == '.')
+      c = '_';
+  }
+  return input;
+}
+
 irep_idt lambda_synthetic_class_name(
   const irep_idt &method_identifier,
   std::size_t instruction_address)
 {
-  return "java::lambda_synthetic_class$" +
-         id2string(strip_java_namespace_prefix(method_identifier)) + "$" +
-         std::to_string(instruction_address);
+  return
+    "java::lambda_synthetic_class$" +
+    escape_symbol_special_chars(
+      id2string(strip_java_namespace_prefix(method_identifier))) +
+      "$" + std::to_string(instruction_address);
 }
 
 /// Retrieves the symbol of the lambda method associated with the given