[Fix/HPHPi] Increase maximum function id

Summary:
To suppress the warning as the number of functions can exceed the current
limit: HipHop Warning: Maximum function id reached: 65536.

Test Plan:
make fast_tests
run server mode flib test and make sure that no warning as shown above.

Reviewers: qigao, mwilliams

Reviewed By: qigao

CC: hphp-diffs@lists, ps, mwilliams, qigao

Differential Revision: 350451

src/runtime/base/runtime_option.cpp

@@ -331,7 +331,7 @@ bool RuntimeOption::CheckSymLink = false;
 bool RuntimeOption::NativeXHP = true;
 int RuntimeOption::ScannerType = 0;
 bool RuntimeOption::SandboxCheckMd5 = false;
-int RuntimeOption::MaxUserFunctionId = 65536;
+int RuntimeOption::MaxUserFunctionId = (2 * 65536);
 
 #ifdef TAINTED
 bool RuntimeOption::EnableTaintWarnings = false;