e-xml: Add C api

Makes it easier to use with C projects (especially those that don't allow C++ code)
You are correct.
Line 14 in build_tools/make_sharedlib.rules
```make
LNK	 		    = $(CC) -shared -Wl,-soname,$(LIBSONAME)
```

This is not trivial to fix since some of your libs are written in C and some in C++.

However, I guess my change is wrong too. It should read:
```patch
+
+# Link with stdc++
+LIBS         += -lstdc++
```
Comments?