bug#26487: Add antlr3

[Julien Lepiller]

Hi, here are patches to add antlr3, a parser generator.

* 0001-guix-ant-build-system-Add-src-dir-parameter.patch: adds a
  #:src-dir parameter to the ant-build-system, to change the source
  directory and possibly specify more than one directory.
* 0002-gnu-Add-antlr2.patch: Adds antlr2, an older version of antlr,
  that is required by antlr3 to generate some of its source files, and
  because parts of it is used by antlr3 (such as the CommonTree class).
* 0003-gnu-Add-stringtemplate3.patch: Adds stringtemplate3, a runtime
  requirement of antlr3. It is a library to generate strings using
  templates.
* 0004-gnu-Add-antlr3-and-stringtemplate4.patch: a big patch that adds
  antlr3 and stringtemplate4 (ST4). ST4 is a newer version of ST3, is a
  runtime dependency of antlr3 and needs antlr3 to generate some of its
  source files. antlr3 depends on ST4 too. I didn't find a way to split
  this patch further.

I wanted to package antlr4, but I'm still working on its dependencies
(antlr3 is one of them).

0001-guix-ant-build-system-Add-src-dir-parameter.patch
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0002-gnu-Add-antlr2.patch
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0003-gnu-Add-stringtemplate3.patch
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0004-gnu-Add-antlr3-and-stringtemplate4.patch
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