fixes #5919 and some other reagent value issues

negative values everywhere.
removes pointless has_reagent() checks

remove_reagent() iterates safely through the holder list already,
unless you need to check a minimum amount,
or simply want to know if it is present, the call is not needed.
typo fix
Added client age restrictions for science jobs.

Raised RD age restriction from 7 to 14
Scientist / Roboticist / Xenoblahblahicist from 0 to 14 as well.
getting rid of text macro
Fixes a few issues with get_wound_type()

Fixes damage causing "healing" wound types that can't bleed.
Fixes flesh wounds not bleeding the instant they heal any damage.
Fixes #5953
airlock/arePowerSystemsOn() refactor

airlock/arePowerSystemsOn() now checks if the airlock has power in
addition to the wires being intact.
Merge pull request #5955 from Walter0o/chem_reag_fix

fixes #5919 and some other reagent issues
Merge pull request #5960 from Ccomp5950/sci-age-limit

Added client age restrictions for science jobs.
Merge pull request #5963 from mwerezak/fixes

Fixes #5953
Merge pull request #5959 from Walter0o/typo_fix

typo fix
fixes #5964
fixes #5970, prevents bugs in the future

this is not an issue at the moment but will become one should maxHealth ever get changed.
Saves 8 MB from the data download. Sorry, Snapshot!
Fixes #5974

- Fixes possible disappearance bug for Laptops
- Fixes breathing not producing CO2. This applied to humans (untested for other races, but probably the same)
Fixes not checking proximity argument
N2 buildup fix attempt. Putting this into separate commit in case it's not wanted.

- Right now, air consists of 20% O2 80% N2 (approx.). Breathing takes O2 and turns it into CO2. CO2 gets scrubbed. Pressure drops, vents refill with air which again contains 80% N2 20% O2.
- This means that only 20% of breathed-out oxygen is replenished. Rest is replaced by N2. In large areas, such as Bar, with many mobs this can eventually lead to dangerous atmosphere status.
- This fix, while OOCly slightly unrealistic handles this issue by turning both O2 and N2 into CO2. Tested in CE's office with 5 human mobs without active scrubbers. Air lasts for 2~ hrs. Larger areas of course last significantly longer.
removes unused AI text2speech files and code,
saves about 4.5 MB traffic per client.