Add the common ".ada" as an accepted file extension.

[Lucretia]

This extension is used in a lot of old Ada source files which contain multiple compilation units.

[masatake]

Could you add following change to your commit?

diff --git a/Tmain/map-removing.d/stdout-expected.txt b/Tmain/map-removing.d/stdout-expected.txt
index 8b582a7e..e8b103fc 100644
--- a/Tmain/map-removing.d/stdout-expected.txt
+++ b/Tmain/map-removing.d/stdout-expected.txt
@@ -9,13 +9,13 @@ MatLab   *.m
 
 [--map-<LANG>] adding *.m to Ada
 =======================================
-Ada      *.adb *.ads *.Ada *.m
+Ada      *.adb *.ads *.Ada *.ada *.m
 MatLab   *.m
 ObjectiveC *.mm *.m *.h
 
 [--map-<LANG>] removing from *.m from ObjectiveC, and adding *.m to Ada
 =======================================
-Ada      *.adb *.ads *.Ada *.m
+Ada      *.adb *.ads *.Ada *.ada *.m
 MatLab   *.m
 
 [--map-<LANG>] guessing parser with adding *.m to Ada

[masatake]

Can I ask you to squash the two commits into one?
Thanks in advance.

[masatake]

Thank you.

[coveralls]

Coverage remained the same at 84.888% when pulling 76114a9 on Lucretia:new-extension into a74b847 on universal-ctags:master.