freebasic support additions

[Glog78]

i had some troubles with the basic ctags so did a small patch which fixed them for me, Here is the patch -> https://termbin.com/m6eb

a.) added declare sub and declare function keywords << not a prefect solution but it makes it so library imported function can be found in the tags. b.) added namespace support so functions and variables show up under there correct namepsace

it's hacky but for me it works okish, Thanks for the work on ctags cause not every language has already lsif or lsp support.

[masatake]

Hi, could you make a pull request for the change? In addition, we need a test case. https://docs.ctags.io/en/latest/testing-parser.html#units-test-facility explains how to write test cases.