Enhancements and improved documentation to the byte-code branch coverage

testing logic.  Provide new macros that allow the code to specify that
some branch instructions can never take the NULL path and that the OP_Jump
opcode is only interested in equal/not-equal.  The
SQLITE_TESTCTRL_VDBE_COVERAGE file control callback now works slightly
differently (it provides the callback with a bitmask of the branch action,
rather than an integer).

FossilOrigin-Name: cd2da7e1ba4e78e68ccf65d4969df963c1e3085930e74419450bda2799381e05

src/sqliteInt.h

@@ -3387,7 +3387,7 @@ struct Sqlite3Config {
   /* The following callback (if not NULL) is invoked on every VDBE branch
   ** operation.  Set the callback using SQLITE_TESTCTRL_VDBE_COVERAGE.
   */
-  void (*xVdbeBranch)(void*,int iSrcLine,u8 eThis,u8 eMx);  /* Callback */
+  void (*xVdbeBranch)(void*,unsigned iSrcLine,u8 eThis,u8 eMx);  /* Callback */
   void *pVdbeBranchArg;                                     /* 1st argument */
 #endif
 #ifndef SQLITE_UNTESTABLE