tests: few tweakings and cosmetic changes * tests/dist-formats.tap: Fix botched spacing. * tests/subobjname.test: Prefer spaces to tabs in indentation. * tests/cond43.test: Likewise. * tests/comment7.test: Likewise. * tests/compile_f90_c_cxx.test: Use "$tab" instead of literal tab characters in the grep regexp. * tests/compile_f_c_cxx.test: Likewise. * tests/pluseq3.test: Likewise. * tests/cond-basic.test: Likewise. * tests/acloca16.test: Add empty line before trailing ':' command. * tests/bsource.test: Likewise. * tests/depend5.test: Likewise. * tests/depend6.test: Likewise. * tests/destdir.test: Likewise. * tests/fort2.test: Likewise. * tests/instdir-java.test: Likewise. * tests/instdir-lisp.test: Likewise. * tests/instdir-python.test: Likewise. * tests/instdir.test: Likewise. * tests/instdir2.test: Likewise. * tests/ltinstloc.test: Likewise. * tests/missing.test: Likewise. * tests/missing2.test: Likewise. * tests/nodef.test: Likewise. * tests/nodef2.test: Likewise. * tests/subst4.test: Likewise. * tests/werror3.test: Likewise. * tests/commen11.test: Likewise. Also, make grepping of automake stderr slightly stricter, and properly quote strings with shell metacharacters. * tests/nodep2.test: Add empty line before trailing ':' command. Do not create unneeded dummy source files.