Usage of __func__ for some ShowMsg.

**Information:**
`__func__` or `__FUNCTION__` returns the function name.

Source: http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html

**Status**: Done

- [x] src/char
- [x] src/common
- [x] src/login
- [x] src/map
- [x] src/plugins

**Example:**
```c
#include <stdio.h>

void potte();

int main(void)
{
    potte();
	printf("%s\n",__func__);
	return 0;
}

void potte()
{
	printf("%s\n",__func__);
}
```

**Output:**
```
potte
main
```
Wouldn't this (re)define `__func__` as `"<Unknown>"` on all C99-compliant compilers?