Fix bitcode parser to check type signatures of functions.

Before, type signatures of functions were only checked when called.
This CL fixes this by checking all function signatures.

BUG=None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1579203002 .

src/IceConverter.cpp

diff --git a/src/IceConverter.cpp b/src/IceConverter.cpp
index 0907167..e54dd2a 100644
--- a/src/IceConverter.cpp
+++ b/src/IceConverter.cpp
@@ -880,6 +880,8 @@
         StrBuf << "\n  Use flag -allow-externally-defined-symbols to override";
       report_fatal_error(StrBuf.str());
     }
+    if (!IceFunc->validateTypeSignature(Ctx))
+      report_fatal_error(IceFunc->getTypeSignatureError(Ctx));
     GlobalDeclarationMap[&Func] = IceFunc;
   }
   // Install global variable declarations.