Add VHDL Support & Newer Verilog Linters (#2229)

* Added VHDL file support with ghdl compiler
* Update ghdl.vim
* Create vcom.vim
* Create xvhdl.vim
* Update xvlog.vim
* Added documentation for VHDL & Verilog linters
* Added tests to VHDL & Verilog linters

test/command_callback/test_ghdl_command_callbacks.vader

@@ -0,0 +1,19 @@
+Before:
+  call ale#assert#SetUpLinterTest('vhdl', 'ghdl')
+
+After:
+  unlet! b:command_tail
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'ghdl', ale#Escape('ghdl') . ' -s  --std=08 %t'
+
+  let b:ale_vhdl_ghdl_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar') . ' -s  --std=08 %t'
+
+Execute(The options should be configurable):
+  let b:ale_vhdl_ghdl_options = '--something'
+
+  AssertLinter 'ghdl', ale#Escape('ghdl') . ' -s  --something %t'

test/command_callback/test_vcom_command_callbacks.vader

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+Before:
+  call ale#assert#SetUpLinterTest('vhdl', 'vcom')
+
+After:
+  unlet! b:command_tail
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'vcom', ale#Escape('vcom') . '  -2008 -quiet -lint %t'
+
+  let b:ale_vhdl_vcom_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar') . '  -2008 -quiet -lint %t'
+
+Execute(The options should be configurable):
+  let b:ale_vhdl_vcom_options = '--something'
+
+  AssertLinter 'vcom', ale#Escape('vcom') . '  --something %t'

test/command_callback/test_vlog_command_callbacks.vader

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+Before:
+  call ale#assert#SetUpLinterTest('verilog', 'vlog')
+
+After:
+  unlet! b:command_tail
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'vlog', ale#Escape('vlog') . '  -quiet -lint %t'
+
+  let b:ale_verilog_vlog_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar') . '  -quiet -lint %t'
+
+Execute(The options should be configurable):
+  let b:ale_verilog_vlog_options = '--something'
+
+  AssertLinter 'vlog', ale#Escape('vlog') . '  --something %t'

test/command_callback/test_xvhdl_command_callbacks.vader

@@ -0,0 +1,19 @@
+Before:
+  call ale#assert#SetUpLinterTest('vhdl', 'xvhdl')
+
+After:
+  unlet! b:command_tail
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'xvhdl', ale#Escape('xvhdl') . '  --2008 %t'
+
+  let b:ale_vhdl_xvhdl_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar') . '  --2008 %t'
+
+Execute(The options should be configurable):
+  let b:ale_vhdl_xvhdl_options = '--something'
+
+  AssertLinter 'xvhdl', ale#Escape('xvhdl') . '  --something %t'

test/command_callback/test_xvlog_command_callbacks.vader

@@ -0,0 +1,19 @@
+Before:
+  call ale#assert#SetUpLinterTest('verilog', 'xvlog')
+
+After:
+  unlet! b:command_tail
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(The executable should be configurable):
+  AssertLinter 'xvlog', ale#Escape('xvlog') . '  %t'
+
+  let b:ale_verilog_xvlog_executable = 'foobar'
+
+  AssertLinter 'foobar', ale#Escape('foobar') . '  %t'
+
+Execute(The options should be configurable):
+  let b:ale_verilog_xvlog_options = '--something'
+
+  AssertLinter 'xvlog', ale#Escape('xvlog') . '  --something %t'