Don't use a symlink where #include would suffice

Absolute symlinks break when the source is moved to another location. In
the best case, the symlink will be replaced with a copy, but that creates
code duplication. A user who got the packaged source may decide to change
one config.c without realizing that another config.c will get the same
changes.

Don't ignore config.c, it's a regular source file now, albeit very
short.

Testing done: compiled inside and outside build directory.

.gitignore

@@ -5,7 +5,6 @@ autom4te.cache/
 ChangeLog
 config_ac.h
 config_ac-h.in
-config.c
 config.guess
 config.log
 config.status

bootstrap

@@ -33,5 +33,4 @@ touch NEWS
 touch AUTHORS
 touch README
 touch ChangeLog
-ln -s ../config.c $PWD/sesman/tools/config.c
 autoreconf -fvi

sesman/tools/config.c

@@ -0,0 +1 @@
+#include "../config.c"