Add argument parsing + switch for uncached operation

This adds support for the following options to cgit:
  --root=<path>
  --cache=<path>
  --nocache
  --query=<querystring>
  --repo=<reponame>
  --page=<pagename>
  --head=<branchname>
  --sha1=<sha1>
  --ofs=<number>

On startup, /etc/cgitrc is parsed, followed by argument parsing and
finally querystring parsing.

If --nocache is specified (or set in /etc/gitrc), caching is disabled and
cgit instead generates pages to stdout.

The combined effect of these two changes makes testing/debugging a lot
less painfull.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

shared.c

@@ -17,6 +17,7 @@ char *cgit_virtual_root = NULL;
 
 char *cgit_cache_root   = "/var/cache/cgit";
 
+int cgit_nocache               =  0;
 int cgit_max_lock_attempts     =  5;
 int cgit_cache_root_ttl        =  5;
 int cgit_cache_repo_ttl        =  5;
@@ -54,6 +55,8 @@ void cgit_global_config_cb(const char *name, const char *value)
 		cgit_logo_link = xstrdup(value);
 	else if (!strcmp(name, "virtual-root"))
 		cgit_virtual_root = xstrdup(value);
+	else if (!strcmp(name, "nocache"))
+		cgit_nocache = atoi(value);
 }
 
 void cgit_repo_config_cb(const char *name, const char *value)