error: strcpy was not declared in this scope
When you say:
#include <cstring>
the g++ compiler should put the <string.h> declarations it itself includes into the std:: AND the global namespaces. It looks for some reason as if it is not doing that. Try replacing one instance of strcpy with std::strcpy and see if that fixes the problem.
Observations:
#include <cstring>should introduce std::strcpy().using namespace std;(as written in medico.h) introduces any identifiers fromstd::into the global namespace.
Aside from using namespace std; being somewhat clumsy once the application grows larger (as it introduces one hell of a lot of identifiers into the global namespace), and that you should never use using in a header file (see below!), using namespace does not affect identifiers introduced after the statement.
(using namespace std is written in the header, which is included in medico.cpp, but #include <cstring> comes after that.)
My advice: Put the using namespace std; (if you insist on using it at all) into medico.cpp, after any includes, and use explicit std:: in medico.h.
strcmpi() is not a standard function at all; while being defined on Windows, you have to solve case-insensitive compares differently on Linux.
(On general terms, I would like to point to this answer with regards to "proper" string handling in C and C++ that takes Unicode into account, as every application should. Summary: The standard cannot handle these things correctly; do use ICU.)
warning: deprecated conversion from string constant to ‘char*’
A "string constant" is when you write a string literal (e.g. "Hello") in your code. Its type is const char[], i.e. array of constant characters (as you cannot change the characters). You can assign an array to a pointer, but assigning to char *, i.e. removing the const qualifier, generates the warning you are seeing.
OT clarification: using in a header file changes visibility of identifiers for anyone including that header, which is usually not what the user of your header file wants. For example, I could use std::string and a self-written ::string just perfectly in my code, unless I include your medico.h, because then the two classes will clash.
Don't use using in header files.
And even in implementation files, it can introduce lots of ambiguity. There is a case to be made to use explicit namespacing in implementation files as well.