allow dynamic configuration of the heap memory (#287)

This PR changes the implementation of the emulated EVM heap memory:
Instead of linking in a C implementation the code is emitted directly
into the contract module. Which allows making it configurable via a
compiler parameter (a follow up PR to this).

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/solidity/src/yul/parser/statement/object.rs

@@ -209,6 +209,8 @@ where
         revive_llvm_context::PolkaVMRemainderFunction.declare(context)?;
         revive_llvm_context::PolkaVMSignedRemainderFunction.declare(context)?;
 
+        revive_llvm_context::PolkaVMSbrkFunction.declare(context)?;
+
         let mut entry = revive_llvm_context::PolkaVMEntryFunction::default();
         entry.declare(context)?;
 
@@ -261,6 +263,8 @@ where
         revive_llvm_context::PolkaVMRemainderFunction.into_llvm(context)?;
         revive_llvm_context::PolkaVMSignedRemainderFunction.into_llvm(context)?;
 
+        revive_llvm_context::PolkaVMSbrkFunction.into_llvm(context)?;
+
         Ok(())
     }