math/asymptote: Unbreak; Update 2.80 -> 2.81

There were 2 breaking problems:

• missing 'gc.h': backport the upstream patch to fix it
• Boost issues: disabled the module lsp that had these issues. Had to update version because lsp wasn't disableable previously.

Approved by: portmgr (unbreak)

(cherry picked from commit 4ec705d832c40fa44a4db9f39d378493dd31b74b)