Simpified attribute wildcard creation and assignment to get rid of memory
* xmlschemas.c include/libxml/schemasInternals.h test/schemas/bug152470_1.* result/schemas/bug152470_1_1*: Simpified attribute wildcard creation and assignment to get rid of memory leaks. Restructured the validation process. Restructured and expanded parsing of <attributeGroup>. Added initial handing of xsi:type. Advanced handling of xsi:nil (should work now for simple types). Added construction of schemata using xsi:schemaLocation and xsi:noNamespaceSchemaLocation; this is not enabled, since no corresponding API exists yet. Moved the content model to complex type components. Resolution of types for attributes will look for simple types only (incl. all the built-in simple types). Extended parsing of 'anyAttribute'. Fixed content-type type for complex types if derived from 'anyType' using the short-hand form (see bug # 152470, submitted by Thilo Jeremias). * include/libxml/xmlschematypes.h: Cleaned u...