fixed build errors, warnings and made a bit more robust

Author: rindeal

premake4.lua

@@ -112,7 +112,7 @@ solution "SQLite3"
   }
   defines {
     "_WINDOWS",
-    "SQLITE_THREADSAFE=2",                  -- http://www.sqlite.org/compile.html#threadsafe
+    "SQLITE_THREADSAFE=1",                  -- http://www.sqlite.org/compile.html#threadsafe
     "SQLITE_DEFAULT_PAGE_SIZE=4096",        -- better performance
     "SQLITE_TEMP_STORE=2",                  -- http://www.sqlite.org/tempfiles.html#tempstore
     "SQLITE_DEFAULT_TEMP_CACHE_SIZE=1024",  -- http://www.sqlite.org/tempfiles.html#otheropt
@@ -231,6 +231,6 @@ solution "SQLite3"
     }
     links { PRJ_NAME_LIB }
     defines {
-      "SQLITE_THREADSAFE=0", -- CLI is always single threaded, generates warnings because of a collision with previous definitions
+      -- "SQLITE_THREADSAFE=0", -- CLI is always single threaded, generates warnings because of a collision with previous definitions
       "SQLITE_ENABLE_EXPLAIN_COMMENTS"
     }

src/sqlite3.c

@@ -136983,7 +136983,7 @@ SQLITE_PRIVATE int sqlite3Fts3EvalPhrasePoslist(
   if( iDocid!=pCsr->iPrevId || pExpr->bEof ){
     int rc = SQLITE_OK;
     int bDescDoclist = pTab->bDescIdx;      /* For DOCID_CMP macro */
-    int iMul;                     /* +1 if csr dir matches index dir, else -1 */
+    /* int iMul;                     /* +1 if csr dir matches index dir, else -1 */
     int bOr = 0;
     u8 bEof = 0;
     u8 bTreeEof = 0;

src/sqlite3secure.c

@@ -7,7 +7,7 @@
 
 // Enable the user authentication feature
 #ifndef SQLITE_USER_AUTHENTICATION
-#define SQLITE_USER_AUTHENTICATION
+#define SQLITE_USER_AUTHENTICATION 1
 #endif
 
 #include "sqlite3.c"