Replaced builtin linker configs with ordinary .cfg files.

The benefits are:
- Independency of ld65 build from perl
- More transparent behaviour

cfg/apple2-asm.cfg

@@ -0,0 +1,20 @@
+# Configuration for assembler programs which don't need a special setup
+
+FEATURES {
+    STARTADDRESS: default = $0803;
+}
+SYMBOLS {
+    __LOADADDR__: type = weak, value = __CODE_RUN__;
+    __LOADSIZE__: type = weak, value = __BSS_RUN__ - __CODE_RUN__;
+}
+MEMORY {
+    HEADER: file = %O, start = $0000, size = $0004;
+    RAM:    file = %O, start = %S,    size = $C000 - %S;
+}
+SEGMENTS {
+    EXEHDR: load = HEADER, type = ro,  optional = yes;
+    CODE:   load = RAM,    type = rw,  optional = yes, define = yes;
+    RODATA: load = RAM,    type = ro,  optional = yes;
+    DATA:   load = RAM,    type = rw,  optional = yes;
+    BSS:    load = RAM,    type = bss, optional = yes, define = yes;
+}