Remove wrapper functions for standard C library functions

[matt335672]

At the moment, we're using wrapper functions for many OS-specific (or OS-variant) calls.

I'm proposing we remove the wrapper functions for functions in C99 standard includes. So for example, g_printf() (duplicates printf() in stdio.h) would go, as would g_memcpy() (duplicates memcpy() in string.h).

Advantages:-

1. the compiler can more easily optimise some of these calls (particularly memcpy()).
2. Lowers the barrier for contributions from the community.
3. Removes unnecessary code

Disadvantages:-

1. Some functions we've implemented have extra guards in them (see for example g_strcpy()). Extra care needs to be taken with these.

Thoughts? Is C99 the right standard to aim for?

[jsorg71]

Yes, this has been on the todo list for a while too. Originally, all the xrdp c files did not include any standard c header files and everything was done through os_call.c, thread_calls.c, etc. The namespace was very clean. Eventually enough contributors complained about things like NULL missing so we started including stdlib.h, stdio.h and string.h. This made most of the wrapping unnecessary. I think the only use now would be for if a function still needs defines. As the comment in os_calls say, put all the defines in there so you don't need then in the main code files. Also I guess if we want extra checks on a call to save code.

To make this easier we can change some calls to macros like #define g_memset memset and #define g_memcpy memcpy
Then we can change them at our own pace and get the compile optimize benefits right away.
all g_malloc calls should be changed to g_new and g_new0.
g_free can be a define too.

Also, I have come to regret the g_ prefix once I mixing gtk / gdk headers with os_calls.h. We should have used os_ prefix or maybe xr_