Switched default compiler to gcc. Fixed #2.

Signed-off-by: New-Guy <Kenneth.E.Sills@Gmail.com>
Added previously missing Doxygen config file (cxtc).

Signed-off-by: New-Guy <Kenneth.E.Sills@Gmail.com>
Added platform-specificity to declarations of xterm and conemu only
functions.

Signed-off-by: New-Guy <Kenneth.E.Sills@Gmail.com>
Added stub implementations for all library functions to allow
compilation.
Fixed incorrect platform specification in input.cpp.

Signed-off-by: New-Guy <Kenneth.E.Sills@Gmail.com>