Undo support for v variable definitions

See the `README.md` change.
I was too eager to enable things without actually checking if they work.
Partially reverts 2374ff1 (#6)

README.md

@@ -62,7 +62,6 @@ exit !bytes.zero? # `#qoi_write` returns 0 on failure
 * Miscellaneous
   * `t` typedefs
   * `x` external and forward variable declarations
-  * `v` variable definitions
 
 ### 📝 Developing
 * Structs/Unions
@@ -95,7 +94,9 @@ exit !bytes.zero? # `#qoi_write` returns 0 on failure
 
 ### 🧊 Nope
 * Non-literal Macros (i.e., C code macros)
-* Miscellaneous Ctags Kinds
+* Miscellaneous u-ctags Kinds
+  * `v` variable definitions
+    * Unlike `x`, these are not exported to dynamic libraries (`.so`s).
   * `l` local variables
   * `L` goto labels
 

lib/ffi/uctags.rb

@@ -88,7 +88,7 @@ def ffi_const(name)
     def call(library_name, header_path, &blk)
       instance = new(library_name)
       #noinspection SpellCheckingInspection this command use letter flags
-      cmd = %w[ctags --language-force=C --param-CPreProcessor._expand=1 --kinds-C=defgmpstuvxz --fields=NFPkSst --fields-C={macrodef} -nuo -] #: Array[_ToS]
+      cmd = %w[ctags --language-force=C --param-CPreProcessor._expand=1 --kinds-C=defgmpstuxz --fields=NFPkSst --fields-C={macrodef} -nuo -] #: Array[_ToS]
       cmd.insert(2, '-V') if $DEBUG
       cmd << header_path
       # Run and pipe-read. `err: :err` connects command stderr to Ruby stderr
@@ -385,7 +385,7 @@ def process(k, name, fields)
       typedef name.to_sym
     when 'd' # macro definitions
       # https://github.com/ParadoxV5/FFI-UCtags/issues/2
-    when 'x', 'v' # external and forward variable declarations, variable definitions
+    when 'x' # external and forward variable declarations
       new_construct
       @library.attach_variable name, extract_and_process_type
     else