dispatch: stop using _mesa_create_exec_table_es1() for GLES1.

dispatch: stop using _mesa_create_exec_table_es1() for GLES1.

This patch modifies context creation code for GLES1 to use
_mesa_create_exec_table() (which is used for all other APIs) instead
of the GLES1-specific _mesa_create_exec_table_es1().

There is a slight change in functionality.  As a result of a mistake
in the code generation of _mesa_create_exec_table_es1(), it does not
include glFlushMappedBufferRangeEXT or glMapBufferRangeEXT (this is
because when support for those two functions was added in commit
762d9ac, src/mesa/main/APIspec.xml wasn't updated).  With this patch,
glFlushMappedBufferRangeEXT and glMapBufferRangeEXT are properly
included in the dispatch table.  Accordingly, dispatch_sanity.cpp is
modified to expect these two functions to be present.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
v2: Leave GLES1.1 dispatch sanity test disabled when not building
GLES1 support.