DataFrame.eval column creation slow due to overhead
#### Code Sample, a copy-pastable example if possible

```python
df = pd.DataFrame({'a':np.random.uniform(size=int(1e7)), 
                   'b':np.random.uniform(size=int(1e7))})

%%timeit
df['c'] = df['a'] + df['b']
41.7 ms ± 2.78 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

%%timeit
df.eval('c = a + b', inplace = True)
68.8 ms ± 6.02 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
```
```python
%prun -l 4 df.eval('c = a + b', inplace = True) 

         3548 function calls (3490 primitive calls) in 0.061 seconds

   Ordered by: internal time
   List reduced from 390 to 4 due to restriction <4>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        7    0.039    0.006    0.039    0.006 {method 'copy' of 'numpy.ndarray' objects}
        1    0.012    0.012    0.012    0.012 blocks.py:335(set)
        1    0.006    0.006    0.006    0.006 necompiler.py:765(evaluate)
      585    0.000    0.000    0.000    0.000 {built-in method builtins.isinstance}

%prun -l 4 df['c'] = df['a'] + df['b']
 
         638 function calls (636 primitive calls) in 0.037 seconds

   Ordered by: internal time
   List reduced from 160 to 4 due to restriction <4>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.014    0.014    0.014    0.014 blocks.py:335(set)
        2    0.014    0.007    0.014    0.007 {method 'copy' of 'numpy.ndarray' objects}
        1    0.007    0.007    0.007    0.007 necompiler.py:765(evaluate)
        1    0.000    0.000    0.014    0.014 managers.py:1019(set)
```
#### Problem description

Column creation with DataFrame.eval seems to be slower (in this dummy example only somewhat slower, but in my "real-world" case it was slower by a factor of 4), because it is making a lot of calls to copy for numpy.ndarray. Also see [here](https://stackoverflow.com/questions/38725355/when-to-use-dataframe-eval-versus-pandas-eval-or-python-eval)

#### Expected Output

#### Output of ``pd.show_versions()``

<details>
```

INSTALLED VERSIONS
------------------
commit: None
python: 3.7.3.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-862.3.2.el7.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.24.2
pytest: None
pip: 19.0.3
setuptools: 40.8.0
Cython: None
numpy: 1.16.2
scipy: 1.2.1
pyarrow: None
xarray: None
IPython: 7.4.0
sphinx: None
patsy: 0.5.1
dateutil: 2.8.0
pytz: 2018.9
blosc: None
bottleneck: 1.2.1
tables: None
numexpr: 2.6.9
feather: None
matplotlib: 3.0.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml.etree: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None
```
</details>