orm: add mysql support (#9630)

* add mysql to orm

* fix got to big packet error

* format sql.v

* format example

* custom sql types

* add mysql table cration

* add documentation

* format sql.v

* fix markdown

* start implementing select_expr for mysql

* remove orm.c

* format sql.v

* finish mysql expr

* remove c

* remove unessecary files

* change to c implementation

* remove c

* added str interpolation for idents

* fix string insert

* fix compilation problems

* fix gitly compilation

* fix typing mistake

* add link to orm docs

doc/docs.md

@@ -3147,8 +3147,8 @@ fn test() []int {
 
 (This is still in an alpha state)
 
-V has a built-in ORM (object-relational mapping) which supports SQLite,
-and will soon support MySQL, Postgres, MS SQL, and Oracle.
+V has a built-in ORM (object-relational mapping) which supports SQLite and MySQL,
+but soon it will support Postgres, MS SQL, and Oracle.
 
 V's ORM provides a number of benefits:
 
@@ -3164,20 +3164,26 @@ import sqlite
 
 struct Customer {
 	// struct name has to be the same as the table name (for now)
-	id        int // a field named `id` of integer type must be the first field
-	name      string
+	id        int    [primary; sql: serial] // a field named `id` of integer type must be the first field
+	name      string [nonull]
 	nr_orders int
-	country   string
+	country   string [nonull]
 }
 
 db := sqlite.connect('customers.db') ?
+
+// you can create tables
+// CREATE TABLE IF NOT EXISTS `Customer` (`id` INTEGER PRIMARY KEY, `name` TEXT NOT NULL, `nr_orders` INTEGER, `country` TEXT NOT NULL)
+sql db {
+	create table Customer
+}
+
 // select count(*) from Customer
 nr_customers := sql db {
 	select count from Customer
 }
 println('number of all customers: $nr_customers')
 // V syntax can be used to build queries
-// db.select returns an array
 uk_customers := sql db {
 	select from Customer where country == 'uk' && nr_orders > 0
 }
@@ -3200,7 +3206,7 @@ sql db {
 }
 ```
 
-For more examples, see <a href='https://github.com/vlang/v/blob/master/vlib/orm/orm_test.v'>vlib/orm/orm_test.v</a>.
+For more examples and the docs, see <a href='https://github.com/vlang/v/tree/master/vlib/orm'>vlib/orm</a>.
 
 ## Writing Documentation