Improvements to C/C++ analysis

General improvements

Query	Tags	Purpose
Cast between HRESULT and a Boolean type (`cpp/hresult-boolean-conversion`)	external/cwe/cwe-253	Finds logic errors caused by mistakenly treating the Windows `HRESULT` type as a Boolean instead of testing it with the appropriate macros. Enabled by default.
Setting a DACL to `NULL` in a `SECURITY_DESCRIPTOR` (`cpp/unsafe-dacl-security-descriptor`)	external/cwe/cwe-732	This query finds code that creates world-writable objects on Windows by setting their DACL to `NULL`. Enabled by default.
Cast from char* to wchar_t*	security, external/cwe/cwe-704	Detects potentially dangerous casts from char* to wchar_t*. Enabled by default on LGTM.

Query	Expected impact	Change
Resource not released in destructor	Fewer false positive results	Placement new is now excluded from the query.
Missing return statement (`cpp/missing-return`)	Visible by default	The precision of this query has been increased from 'medium' to 'high', which makes it visible by default in LGTM. It was 'medium' in release 1.17 and 1.18 because it had false positives due to an extractor bug that was fixed in 1.18.
Missing return statement	Fewer false positive results	The query is now produces correct results when a function returns a template dependent type.
Call to memory access function may overflow buffer	More correct results	Array indexing with a negative index is now detected by this query.
Suspicious add with sizeof	Fewer false positive results	Arithmetic with void pointers (where allowed) is now excluded from this query.
Wrong type of arguments to formatting function	Fewer false positive results	False positive results involving typedefs have been removed. Expected argument types are determined more accurately, especially for wide string and pointer types. Custom (non-standard) formatting functions are also identified more accurately.