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/main.c

@@ -3974,7 +3974,8 @@ int sqlite3_test_control(int op, ...){
     */
     case SQLITE_TESTCTRL_VDBE_COVERAGE: {
 #ifdef SQLITE_VDBE_COVERAGE
-      typedef void (*branch_callback)(void*,int,u8,u8);
+      typedef void (*branch_callback)(void*,unsigned int,
+                                      unsigned char,unsigned char);
       sqlite3GlobalConfig.xVdbeBranch = va_arg(ap,branch_callback);
       sqlite3GlobalConfig.pVdbeBranchArg = va_arg(ap,void*);
 #endif