Vasil Velichkov

Add EXTERNAL support

3

Fixes #140 Fixes #294 - Regenerate asn1p_l.c and asn1p_y.[ch] with (f)lex and bison/yacc - Remove asn1p_l.c, asn1p_y.c and asn1_p.h from the repository. - Bison 3 no longer supports YYPARSE_PARAM and...

Add some more C++ extensions

4

[Google C++ style guide](https://google.github.io/styleguide/cppguide.html#File_Names) requires `.cc` extension and also `gcc` supports [few more extensions](https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Overall-Options.html#Overall-Options) - `.cxx`, `.CPP`, `c++`, `.cp` and `.C` Also improve the testing instructions in the README.md