[Bug-apl] Error building libapl

[Rowan Cannaday]

Hello!

I am trying to compile libapl, and am running into the following error:

```
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I.. -Wall -I sql -Wold-style-cast -Werror -I/usr/include -I/usr/include/postgresql -rdynamic -g -O2 -MT libapl_la-libapl.lo -MD -MP -MF .deps/libapl_la-libapl.Tpo -c libapl.cc  -fPIC -DPIC -o .libs/libapl_la-libapl.o
libapl.cc: In function 'Value* get_value(APL_value, uint64_t)':
libapl.cc:210:4: error: 'Z' was not declared in this scope
    Z.get()->increment_owner_count(LOC);   // keep value
```

I am using the following to configure:
```
./configure --with-libapl
```
 
I have built the interpreter successfully before.

I also generated a tags file for the project and it is unable to find the definition for 'Z'.

Any help is appreciated, thank you for your time!