1 change the default value of max_dso_module to 256.
2 add the option of setting max_dso_module.
1 fixed the bug of generating makefile in dso module.
2 determine the return code of make command in dso module.
fixed some code style.
fixed the bug for duplicate module of the module_stubs when install
nginx(enable dso).
Merge pull request #426 from monadbobo/dso_fix14

1 change the default value of max_dso_module to 256.