Always pop the l-value on variable declaration.

Otherwise, it might lead to unexpected behaviour including protected memory access and segmentation fault.
This finally fixes #49.

engine/compiler.c

@@ -2555,6 +2555,8 @@ static sxi32 PH7_CompileVar(ph7_gen_state *pGen) {
 			void *p3 = (void *) zDup;
 			/* Emit OP_DECLARE instruction */
 			PH7_VmEmitInstr(pGen->pVm, pGen->pIn->nLine, PH7_OP_DECLARE, 0, nType, p3, 0);
+			/* Pop the l-value */
+			PH7_VmEmitInstr(pGen->pVm, nLine, PH7_OP_POP, 1, 0, 0, 0);
 			/* Check if we have an expression to compile */
 			if(pGen->pIn < pGen->pEnd && (pGen->pIn[2].nType & PH7_TK_EQUAL)) {
 				/* Compile the expression */