* gdb.base/attach.exp, gdb.base/detach.exp, gdb.base/gcore.exp,
gdb.mi/mi-basics.exp, gdb.threads/gcore-thread.exp,
gdb.trace/save-trace.exp: Make sure that full pathnames are
escaped correctly.
* mi-basics.exp: Change tests for -environment-directory. Also add
tests for -environment-cd, -environment-pwd, and -environment-path.
Part of fix for PR gdb/741.