use of `@eval` inhibits performance

[vtjnash]

This code should not use @eval, since changing the dispatch table can have poorly-controlled side effects:

HTTP.jl/src/Handlers.jl

Lines 410 to 417 in 209f10e

	@eval function HTTP.Handlers.gethandler(r::$(Expr(:$, :(typeof($router)))),
	::(HTTP.Handlers.gh($method)),
	::(HTTP.Handlers.gh($scheme)),
	::(HTTP.Handlers.gh($host)),
	$(Expr(:$, vals)),
	args...)
	return $(Expr(:$, handler)) isa HTTP.Handler ? $(Expr(:$, handler)) : HTTP.Handlers.RequestHandlerFunction($(Expr(:$, handler)))
	end

[eliascarv]

I'm dealing with issues generated by this function.

using HTTP

const router = HTTP.Router()

function test_register(router, method, path, handler)
    HTTP.@register(router, method, path, handler)
end

function test_handler(req::HTTP.Request)
    return HTTP.Response(200, "test")
end

test_register(router, "GET", "/test", test_handler)

ERROR: LoadError: UndefVarError: method not defined
Stacktrace:
 [1] top-level scope
   @ none:1
in expression starting at c:\Users\User\Documents\Elias\HTTP\test.jl:13