[Bug cli/23138] New: add a "usage" command

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=23138

Bug ID: 23138
Summary: add a "usage" command
Product: gdb
Version: 8.0.1
Status: NEW
Severity: normal
Priority: P2
Component: cli
Assignee: unassigned at sourceware dot org
Reporter: tromey at sourceware dot org
Target Milestone: ---

Once most commands have a "Usage:" line in their help text,
gdb could have a "usage" command that would work like "help"
but just print the usage summary.