Add more patterns to .gitignore files

A number of patterns and filenames where missing from .gitignore files,
especially in the tests/ directory.

.gitignore:
boehm_gc/.gitignore:
boehm_gc/libatomic_ops/pkgconfig/.gitignore:
runtime/.gitignore:
scripts/.gitignore:
tests/.gitignore:
tests/analysis/table/.gitignore:
tests/analysis/trail/.gitignore:
tests/benchmarks/.gitignore:
tests/debugger/.gitignore:
tests/invalid/.gitignore:
tests/mmc_make/.gitignore:
tests/mmc_make/lib/.gitignore:
    Add new patterns to .gitignore files.

    Remove some patterns that are implicit because they're in a parent
    directory's file.

tests/analysis/.gitignore:
    After removing superfluous patterns this file was empty.  I've deleted
    it.

.gitignore

@@ -16,6 +16,7 @@ Mmake.stage.params
 stage1
 stage2
 stage3
+install_grade_dir.*
 Mercury.options
 autom4te.cache
 aclocal.m4