Fix #129: Strip quotes from SIP parameter values in parser

The generic SIP parameter parser (_parse_gen_params) was including the
surrounding double-quotes as part of quoted parameter values. For
example, boundary="myboundary" was stored as "myboundary" (with quotes)
instead of myboundary (without quotes).

This caused multipart MIME body parsing to fail because
findNextBoundary() searched for "--\"myboundary\"" in the body instead
of "--myboundary", resulting in "unexpected end-of-buffer" errors.

The fix adjusts the VP_PVALUE_QUOTED state handling to skip past the
opening quote when recording the value start position, and to stop
before the closing quote when recording the value end position.

This has no impact on other SIP parameters (tag, branch, received,
rport, lr, transport) as they are always tokens and never quoted.

Author: marcel

core/sip/parse_common.cpp

@@ -201,7 +201,7 @@ static int _parse_gen_params(list<sip_avp*>* params, const char** c,
 
 	    case '\"':
 		st = VP_PVALUE_QUOTED;
-		beg = *c;
+		beg = *c + 1;
 		break;
 
 	    case ';':
@@ -250,7 +250,7 @@ static int _parse_gen_params(list<sip_avp*>* params, const char** c,
 
 	    case '\"':
 		st = VP_PARAM_SEP;
-		avp->value.set(beg,*c+1-beg);
+		avp->value.set(beg,*c-beg);
 		params->push_back(avp.release());
 		avp.reset(new sip_avp());
 		break;