Update the shawnw-math patch + small readme how to deal with patches

Author: mindreframer

diffs/Readme.md

@@ -0,0 +1,14 @@
+$ cp src/sqlite3-shawnw_math.c src/sqlite3-shawnw_math-fixed.c
+
+## fix src/sqlite3-shawnw_math-fixed.c...
+
+$ diff -u src/sqlite3-shawnw_math.c src/sqlite3-shawnw_math-fixed.c > diffs/sqlite3-shawnw_math.diff
+$ rm src/sqlite3-shawnw_math-fixed.c
+
+## apply patch (-p0 to handle folders!)
+
+`patch -p0 < diffs/sqlite3-shawnw_math.diff`
+
+## reverse patch
+
+`patch -p0 -R < diffs/sqlite3-shawnw_math.diff`

diffs/sqlite3-shawnw_math.diff

@@ -1,5 +1,14 @@
---- src/sqlite3-shawnw_math.c	2021-10-15 15:22:32.000000000 +0200
-+++ src/sqlite3-shawnw_math.c	2021-10-15 15:04:03.000000000 +0200
+--- src/sqlite3-shawnw_math.c	2021-10-15 17:56:04.000000000 +0200
++++ src/sqlite3-shawnw_math-fixed.c	2021-10-15 17:55:42.000000000 +0200
+@@ -28,7 +28,7 @@
+ #include <stdlib.h>
+ #include <string.h>
+ 
+-#include <sqlite3ext.h>
++#include "sqlite3ext.h"
+ SQLITE_EXTENSION_INIT1
+ 
+ static void mf_deg(sqlite3_context *p, int nArg __attribute__((unused)),
 @@ -1402,7 +1402,7 @@
  #ifdef _WIN32
  __declspec(dllexport)