BaseTools/VfrCompile: report error for Integer overflow

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1415

When an integer constant specified in the .vfr file is
too large for the varstore field it is being used with,
the VFR compiler reports an overflow warning like this:
Test.vfr(693): WARNING: Overflow: Value 1024 is too large to
         store in a UINT8
    : String to UINT* Overflow
Since Warning does not break the build process,
and it is easy to miss it.
This patch is to update the code to report error and break
the build if meet this kind of issue.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/C/VfrCompile/VfrError.cpp

@@ -47,12 +47,12 @@ static SVFR_ERROR_HANDLE VFR_ERROR_HANDLE_TABLE [] = {
   { VFR_RETURN_CONSTANT_ONLY, ": only constant is allowed in the expression"},
   { VFR_RETURN_VARSTORE_NAME_REDEFINED_ERROR, ": Varstore name is defined by more than one varstores, it can't be referred as varstore, only varstore strucure name could be used."},
   { VFR_RETURN_BIT_WIDTH_ERROR, ": bit width must be <= sizeof (type) * 8 and the max width can not > 32" },
+  { VFR_RETURN_STRING_TO_UINT_OVERFLOW, ": String to UINT* Overflow"},
   { VFR_RETURN_CODEUNDEFINED, ": undefined Error Code" }
 };
 
 static SVFR_WARNING_HANDLE VFR_WARNING_HANDLE_TABLE [] = {
   { VFR_WARNING_DEFAULT_VALUE_REDEFINED, ": default value re-defined with different value"},
-  { VFR_WARNING_STRING_TO_UINT_OVERFLOW, ": String to UINT* Overflow"},
   { VFR_WARNING_ACTION_WITH_TEXT_TWO, ": Action opcode should not have TextTwo part"},
   { VFR_WARNING_OBSOLETED_FRAMEWORK_OPCODE, ": Not recommend to use obsoleted framework opcode"},
   { VFR_WARNING_CODEUNDEFINED, ": undefined Warning Code" }