Input / output

• sgs_Get(Err)OutputFunc - return the current output callback and its user data pointer
• sgs_Set(Err)OutputFunc - set the output callback and its user data pointer
• sgs_(Err)Write - pass a character buffer to the output callback
• sgs_(Err)Writef - pass a formatted string to the output callback
• sgs_(Err)WriteStr - pass a null-terminated string to the output callback
• sgs_GetMsgFunc - return the current messaging callback and its user data pointer
• sgs_SetMsgFunc - set the messaging callback and its user data pointer
• sgs_Msg - invoke the messaging system
• sgs_WriteErrorInfo - write message info to output callback
• sgs_PushErrorInfo - push message info to stack
• sgs_HasFuncName - check if current C function has a name set
• sgs_FuncName - set current C function name
• SGSFN - set current C function name
• SGSBASEFN - set current C function name if it's not already set
• sgs_Errno - copy errno to internal errno if 2nd argument is false, otherwise clear it
• sgs_SetErrno - set the internal errno value
• sgs_GetLastErrno - return the currently set internal errno value
• sgs_StdOutputFunc - example output callback
• sgs_StdMsgFunc_NoAbort - example messaging callback that does not abort on errors
• sgs_StdMsgFunc - example messaging callback
• sgs_Cntl - set and/or retrieve various states in the system
• sgs_ArgErrorExt - emit an argument type mismatch error with additional formatting options
• sgs_ArgError - emit an argument type mismatch error
• sgs_FuncArgError - emit an argument type mismatch error (alias for states where this variable is hidden)
• sgs_MethodArgError - emit an argument type mismatch error (alias for states where this variable is NOT hidden)