BaseTools:ECC report errors on account of analyze special characters

BaseTools:ECC report errors on account of analyze special characters

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=1751

In case that a C function body contains the string of L'', L'\"',
L"\"", L''', L""", L"\"\"", L"\"^", L" \"", L"\" \"", ('L",\\\""')
ECC tool running under python3 interpreter will report error.
The antlr4 module misidentified this character

This patch is going to fix that issue.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>